Why won't he have sex with me?

So lately we haven't had sex for over 5 months and it's really getting to me cuz when we first started dating we would have sex anywhere in the car or at his house the thing is his parents live there so we only do when they weren't there and at my house to when noyone was there he says that we don't have sex much cuz his parents are always there but he doesn't want to have sex in the car either it really makes me feel like he's not interested me anymore I don't now what do anymore I've been with my boyfriend for 5 years and u believe sex is important in a relationship lately we been arguing bout how he's not intimate wit me but yet he wants me to give him head and all but he won't pleasure me I think it's selfish as hell he doesn't even eat me anymore or anything else that's sexual for that matter pls someone tell me what's going on here or what I should do cuz I've lost my patience