What have I gotten myself into?!?!?!?! HELP!!!!?

Ok.. so I was dating this guy, Preston, for a while and we broke up but remained friends.. Well him and his roommate Ryan needed someone to pick up the other third of the rent since their other roommate was getting married.. So I moved in with them and they both became my best friends.. This was 2 years ago. One night I would hang out with Preston, one night I would hang out with Ryan.. Well Preston and I ended up getting back together last year.. For the past couple month or so the relationship has been kind of rocky to say the least.. We've decided to take a break and see what happens.. He's gotten jealous of the time I spend with Ryan yet he sees no problem with him going out with some of his friends (the majority are girls - and I don't get along too well with them, but they're his friends so I let him go - one of which I know he used to hook up with - once while we were together).. Well last night Preston goes out with a bunch of people and I talk Ryan into going out to get a movie with me and we came back and order a pizza and watched the movie.. The movie goes off and its like, 10:30.. Preston usually don't get home till 2 or 3 when he goes out so we decided to go to bed even though its early.. I go get in the shower and he comes in the bathroom and pretends like he's going to come into the shower with me.. Jokingly I tell him to come on in and he does.. WOW was all I thought.. Even more gorgeous when he's naked lol.. (he looks alot like Alex Rodriguez :) - same gorgeous eyes too) Well one thing leads to another and we end up..well, between the sheets ;) .. He slept in my room until about 5 this morning.. Then he snuck back into his room.. I am so confused.. Should I tell Preston about what happened? I mean, we aren't technically dating right now.. So I don't know if I should.. What should I do with Ryan? I know he used to have a thing for me and I did him but I was dating Preston so nothing came of it.. I haven't seen him yet this morning since he went back to his room.. I don't know what to do!! Help!!! Advice will be greatly appreciated right now...