I [29m] feel like I should break up with my girlfriend [28f] because of lack of sexual chemistry. How can I prevent shredding her self-esteem?

Tldr: I need to tell my girlfriend that the sexual chemistry between us does not work. How do I tell her without completely destroying her self-esteem? Need advice!
So my girlfriend and I have been together for about two years. We have a great emotional and mental bond and get along wonderfully. I realized that for me, the sexual chemistry was really low from the beginning. I thought we could work on that and that it would come with time. Unfortunately it did not and it breaks my heart... We have sex somewhat regularly but usually I'd rather just cuddle and watch a movie or do something else with her. Even things I loved doing with previous partner rather turns me off with her. I can't even go down on her because the taste is irritating and that was something I loved to do.
As hard as it is, I feel like she deserves someone who's as much into her as she is into me. I don't want to end up in a long term relationship where both of us are unsatisfied with our sex life, even if all other domains are well. I feel like I can't give her what she wants and needs.
The thought of breaking up will probably already hurt her very much. She's planning a future with me and talks constantly about moving in together, starting a family etc. I'm afraid that telling her that the sexual chemistry does not work for me will shred her self-esteem and I really want to prevent this. I think my girlfriend is wonderful and beautiful but it somehow doesn't work for me sexually. I had flings with girls which were way below here judging by the looks with which the chemistry was not an issue. So how can I explain this to my girlfriend without completely devastating her? I really hope for some advice!
Edit: Holy... This blew up way more than I thought. I will try to answer as many questions as possible.
So, some clarifications: I am not 100% sure yet if a break-up is the way to go. If it is, I have not accepted it yet just now. I will therefore talk to some people in my support net and try to get some time to think on my own.
People thinking I have not tried working on this: I did. She realised that I am reluctant to sex sometimes. We tried to spice things up with toys, different places, etc. I cut down on self-enjoyment. Hell I am open to seeing a therapist. However, I am not sure if any of these things can affect the sexual chemistry.
Anyway, I will try to make up my mind as soon as possible and let her know as soon as this happend.
Thank you all for your advice! It is really appreciated.


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