I (24F) think my husband (29M) is going to divorce me over Facebook messages I sent in high school. What to do?

Throw away, obviously. I think my husband is going to end things with me, and I'm not really sure what to do next.
My last post was removed because a lack of question. My question is how do I discuss this with him? What can I say that will help him understand that this is not who I am as a person? Or any general advice is welcome as well.
First I want to make it clear that I've always been faithful to him, these messages occurred years before we ever met. We've been together for about 3 and a half years, married for almost 1.
Last night he logged onto my facebook and read messages from when I was in high school. Some of these messages were explicit, however, they were with people I didn't have relationships with. I had never even went out with them, met them, or did anything physically sexual. They were just flirtatious and explicit messages. He woke me up to confront me about them at roughly 4 am last night, and I just deleted them on the spot to avoid him looking at them further. I have no recollection as to what was said, or even who exactly, because it was from 7 or 8 years ago. I never told him about these sexting instances because, well, I never would meet up or do anything with them. I was just being a dumb kid, and I'm not even sure as to why I did it back then. Of course I feel guilty and ashamed now, and my husband has been away at work so we haven't been able to talk much about this. From what he has sent via text message, he clearly doesn't think he can be with me any longer. He's even called me a ****, which really hurts me. He feels lied to, which I can understand because I never told him about these instances. However, I never felt the need to bring them up when talking about past relationships because they were just conversations. He also feels like we don't have any shared values any more, but I want him to understand that values change over time and I'm not the same stupid kid that I was in high school.
Honestly, I'm not sure where to go from here. He'll be off work pretty soon and I know this is something we need to talk about. I just don't really know what to say, and I'm pretty sure our marriage is over because of this. I really don't want things to end, but I don't know how to recover from all of this. Any advice would be appreciated.
Edit: I want to add that he's been a little insecure that we both had the same amount of sex partners prior to getting together (2). Both of his were long term relationships. 1 of mine was long term, and my other one was a 4ish month relationship that I thought was going to be long term. My husband and I met about 2 months after that last relationship and he's always resented my sexual history.
tldr: I think my husband is going to end things due to explicit facebook messages from when I was in high school. What do I do


Source.