Talking to my boyfriend about improving sexually

Every time I try to talk to my boyfriend about improving our sex life he seems to get annoyed and angry, like I'm doing something wrong! I always try and approach it sensitively and inquisitively, asking him his opinion on things rather than telling him what he's doing wrong but he still gets annoyed. I find quite often that if I don't come during sex he will ask if I want him to 'finish me off'... Obviously I do, but the way he phrases it, and the sighs and lack of enthusiasm when I say yes puts me off. He seems to kind of enjoy it when he does, but not fully. I tried to ask him today, by saying "do you enjoy making me come, after we've had sex", and he said he didn't know. It wasn't yes or no. He tried to use examples and ended up indirectly saying that he wishes I'd hurry up and then when I asked if that's what he meant (very casually, almost curiously) he got really annoyed and said I was so negative and I never listen. We ended up arguing and now he's ignoring me because I cried. I just want to talk to him but I don't know how. He says the way I approach it is all wrong so I try different ways. Then I ask different questions, in different tones of voice, different situations. None of it works. And his libido isn't what it was a few months ago. We used to have sex at least once a day and it was amazing and now he's rarely in the mood, and when he is I kind of feel like I'm just satisfying his need, not the other way. He doesn't seem to enjoy any foreplay unless it's on him. I can play with him all of the time, but it doesn't lead anywhere a lot of the time, and he never ever touches me intimately when I ask, and rRely when we have sex. I feel like he's gone off me, I just don't understand why?! How do I talk to him? How do I up his libido? How do I get him to enjoy making me come? Please give me advice if you've done this successfully before?