What should i do-i think what he did is "almost" cheating?

so let me begin by saying my boyfriend (of 2 years) actually does have mental problems stemming from an abusive childhood. i believe he has either asbergers syndrome, bipolar, severe stress issues/anger issues or even all of the above. he is like a child sometimes and literally jut doesnt understand sometimes what he has done wrong (asbergers is a high functioning form of autism and his gramma and i believe he has it) he is supposed to go to psychiatrist soon we are trying to find him an affordable one. okay so on with what happened- well ill call him billy. billy has had many girlfriends. (think more than 10-15)-only about 5 have lasted longer than 3 months. im his longest relationship at 2 years. when i ask why all the relationships fail he says it was the girls most of the time- leaving him for other guys, cheating on him, giving up on him, ect. so his first gf worked down the street from where we live about a year ago and i found out that sometimes after we would get in a fight he would go to her and vent about me. well she soon was telling him to leave me and go out with her and all this ****-she has never even met me. well she moves to college and we would fight about her sometimes b/c he would always defend her saying she was one the best gf's he had. turns out she had left him for another guy and he then started to blame her (along with other girls) for why he is so cold sometimes-they jaded him he says. so a few nights ago while he was having a guys night- me and my friend pretend to be her and text him from my gf's phone-he didnt have her #. i say hey its michelle yadda yadda. well he doesnt give her the time of day-texts back short answers like "cool" and "yeah" and then stops texting her back. i was relieved and so i call him (from my phone) and were all sweet and nice and i tell him im staying at my house that night. i go home to sleep. the next morning my friend calls me and says "omg he called last night at 2 am! AND he sent texts all this morning about meeting up and catching up and doing the beach and he called twice and left a voicemail!" i was shocked!! so i play it cool and call him and he gets mad at me saying he wants me to come up to hang out for a while. i said later i have to do laundry and stuff so he gets mad and says "well michelle texted me ill go hang out with her!" then we calm down and i say "so did she really text you?" and he said "no babe i was lying to get you mad" so im like w/e and i tell him ill call him later. me and my friend immediatly start texting him saying "yeah beach sounds great but i wanna see your house! can i come over to chill around 3:30?" he texts her back saying "yeah!" it was 12:00 when we did this-so he calls me saying "yeah come up now so we can chill and hang out for about an hour-we can do it cuz im horny and you can help me clean the house but then you have to go cuz im going to chill with alex for a while (his friend) i was shocked! i played it cool and said "okay babe" then went right back to texting as his ex. as the ex i said "so are you atill with that bitchy gf of yours?" he says "funny you say that-shes bitchy as ever! not really i mean we talk on the phone sometimes but lets not talk about her-too much heartache for me" so then i say "so shes not your gf?" he texts back "we dont **** anymore" OKAY SO YEAH HE CALLED ME TO COME UP, **** HIM, HELP HIM CLEAN HIS HOUSE FOR THIS ***** AND THEN I LEAVE SO HE CAN CHILL WITH HER AND DO GOD KNOWS WHAT!- I called him right away saying caught you mothererrr and called him out on everything. so then he freaks out on me!! saying im a ***** i have nothing better to do and i wanted this to happen and oh then he says that he was only saying that so he could put her down b/c he told me "i hate her b/c what she did to me so i was gonna lead her on and tell her to **** off you should have kept texing me you dont know what i was gonna say" so yeah! he keeps trying to defend himself! saying "i knew you would get mad and i havent seen her ina while and yeah!" so what the **** do i do now? we have a planned trip to disney this monday the 17th im so heartborken i dunno what to do....