Advice!

My boyfriend and I have been dating for 3 1/2 years. I love him to death, he is absolutely everything to me. I know relationships are hard, I know that relationships require a lot of work. I understand that, but for a while now my boyfriend isn't affectionate towards me at all. When we first began dating it was him always giving me compliments, telling me he loves me without me having to say it first (little things like that). Now I don't get any of that. I have talked to him about him not being affectionate towards me many times and he always says he's sorry and that he'll work on it, so for that day he will be affectionate towards me but after that he goes right back to being non-affectionate and how he normally is. I've asked him if he's lost feelings for me and he says he hasn't, but my mind just can't help thinking that he has because he shows hardly any affection.. I always tell him what he means to me and how much I love him and treat him so well. It would just be nice to get that in return sometimes... What should I do??? Please help???