Boyfriend been arrested... help

I was absolutely horrified when im boyfriend,20, had been arrest accused of attempt rape of a 55 year old woman. I really dont know what to do as i strongly believe he hasnt done it but he has admitted they had sexual contact but then her son walked in a she freaked and cried rape. He really isnt like this at all, thats why im so shocked, it was a drunked night out that ended badly. He is an absolute mess atm and is on suicide watch, he is truly distrusted and is so sorry that hes hurt me, he is an emotional mess and im really worried about him. However at the end of the day he has cheated on me and to top it for i think hes going to go down for attempted rape :( I said to my self in the pass if anyone ever cheats on me id walked away hpwever i feel trapped as he has said that im the only person getting him through this and that he would have ended his life if it wasnt for me :/ I really do love him and i know this was the biffest mistake he has ever made and he is really paying for it but so am i, what should i do?