guy problems/venting

Sooo I have this guy friend, we're also roommates sharing a twin size bed together.. I know sounds weird and probably confusing but it's complicated. Anyway, were really good friends so we tell each other everything. He's been living with me for about 4 months now and honesty yes we have had sex.. more then once. He always initiates it and I'm okay with that cause tbh I actually like it. I don't even like him like that cause I know he likes or is interested in 2 other girls. For awhile I saw it as friends with benefits but last night we had sex and literally right after he got on the phone with a girl he likes and talked for 2.5 hours. It was then when I realized or felt like I'm only good for sex to him (in terms of not good enough for a relationship) cause we do a lot for each other. But like I said I don't like him like that but I just don't understand why he doesn't like me but wants to have sex with me. I feel like since he can't get sex from these girls that he actually likes and potentially wants to get into a relationship with he chooses me to have sex with because he can. It may be my fault for allowing it to happen in the first place but I don't know how to bring this up to him. This morning  when he woke me up at 6:20 so that I could move over cause he was done with his conversation I told him he could sleep somewhere else and he was mad confused. I told him I wasn't gonna talk about it right now cause hello it's 6:30 in the am and I need to be up at 8:30 so he slept on the floor. I just needed to vent about this cause I don't know if I shouldn't spaz on him cause it ispartially my fault or what. I just need someone to hear me out and give me advice. And no him moving out is not an option.