I(25f) broke up with my boyfriend (25m) over a drunk flirty text. Did I overreact?

My boyfriend and I haven't been together very long (6 months) and it's been pretty rocky so far. We started off really hot and heavy, and became really close really quickly. This led to me kind of losing my independence, and coupled with a couple other personal things I was going through, this led to me having a lot of anxiety issues through the first few months of our relationship. Since July or so, though, it's been better and I've regained my independence from him.
Our biggest issue has been my boyfriend's partying tendencies. He is in the beginning stages of addiction (cocaine and alcohol), and although I like to party as well, he does it way too much for what I'm comfortable with. We've had extensive conversations about this issue and I thought we were on the same page, but his actions keep telling me different. He's lied to me twice about doing coke, and he didn't even fess up those times, his friend accidentally outed him.
To be totally honest, the coke wasn't that big of an issue with me, it was the lying about it. He's not waking up and doing it, but he also can't go out and drink without getting some. I've told him I refuse to be his keeper, and he needs to be a grown man and make his own decisions, but also that if he keeps going down this path I can't be with him anymore. The last time we had a come-to-jesus talk about his habits was last Monday, where I was fully ready to break it off and he told me he needed one more chance and that he would seriously stop partying so hard.
Wednesday night, he went out after work, but was supposed to come and stay at my house afterwards. At 2 AM I woke up and he wasn't there yet, so I tried calling him and his phone was off. I was pretty heated, but honestly, it happened more than once in the past where he went and crashed at his friends house by the bar/his work because he didn't want to drive. He called me at 7 AM and told me he slept in his truck because he didn't want to drive. I was annoyed and didn't think it showed good faith efforts towards not partying anymore, but I believed him and moved on.
This past weekend, I was gone Friday night camping and all day Saturday for a friend's birthday. I asked him what he was up to and he said just hanging at a friend's house drinking. I was cool with it, and I didn't ask him if he got any blow because I didn't really want to hear the answer.
Now, some backstory on the girl he sent this text to. Before we dated, we were just ****-buddies and would make some crude jokes about it. I was determined to keep it casual between us and maybe I was a bit too adamant about it, but whatever. We were out drinking and we walked toward this girl and before we get to her (we'll call her C) he goes, "I wanted to bang this girl for awhile but she never let me". He said it very casually and I know it wasn't meant to intentionally hurt me, but I think he took the casual thing too far and my insecurities flared up. She was very nice, and still is. After we started dating, we ran into her one time at a bar (again) and I couldn't help but feel insecure/jealous and honestly just wanted him to be attached at my hip because I didn't trust him around her.
Some more background about him: He's pretty flirtatious, and has a reputation for being so. I'm honestly pretty okay with it, as long as there's a line. I've told him I don't want any girl to feel like she has something behind my back with him. Basically, don't make any girl feel like she's genuinely special to you. I think that's fair. Being nice and flirtatious is one thing, but leading a girl to believe that you want her is another thing completely. I digress. There have been a couple of times where I had to establish what boundaries I was comfortable with when it came to his flirting, but he was always eager to work with me and knew that sometimes it wasn't appropriate and agreed. Because we've had issues in the past, he's given me permission to look at his texts because he wants me to be able to trust him. The past couple times he's been pretty clean, and I really only went through it when he lied to me about blow because that's when my trust for him was lowest.
Yesterday, I went through his phone and found a texting convo between him and C, dated wednesday night at 1 AM. Basically the gist was this:
BF: C!!!!
C: Hey I'm in ______ with no ride
BF: oooo, ________
C: something something i'll come hang
BF: something something ok hot stuff
C: shut up i'll see you in half an hour
And I was pretty livid. He swears up and down that she didn't end up coming to hang and that he never saw her at all that night, but I just can't believe him. I ask him what the hell he was thinking and he said basically that he wasn't. He's apologized more than enough, but i just feel... betrayed and honestly the same as if he had cheated. I'm going to get an STD test because I can't trust him. He's admitted to being stupid and selfish and careless, and I don't really see how we can come back from this without me having to watch his every move which just isn't fun for anybody. I should probably just let it go and chalk it up to his sucking but I guess I need validation that I'm not overreacting, and maybe advice on how to communicate/think the healthiest through all of this.
I suppose the biggest redeeming quality of the relationship and why I even feel like maybe we should fix it is because I really was very hard to deal with the first few weeks/two months of our relationship. I had more than one anxiety attack and he couldn't have been more helpful through all of it. I know that he's a good person who just has issues he needs to work through and I can relate, because I'm working through mine as well. He's not lazy, he's genuinely sweet and compassionate and I do love a lot of things about him, but this is all v fresh and confusing. I'm still working through a lot of anger about it and I'm unsure if I should stick with my gut or if my gut is too controlling.
TL;DR: my boyfriend has tendencies of hiding things and being kind of shady, i found text messages that I was very hurt by and now I'm unsure if I've overreacted
Edit: thanks guys. Sometimes it’s hard to see the truth even though you know it. I’m better off alone and he can eat ****


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