Age problems

Foxy
I'm seeing this guy, and we're having really great sex, which we both like. But every time my age crops up (I am 17 he is 20) I can see he gets really uncomfortable. Last night he reduced me and what we had to "just fun", which I found patronising and hurting, since I'm more mature than that and I never wanted any relationship anyway! 
I called him 'baby' as I flirt and joke (that's how I am with everyone) and he said 'don't call me baby'. I don't know what to do, it's really starting to make me irritated and disappointed in him! 
I also don't want to be reduced to 'some fun' because we get on really well when we're together and I just want to let him know that! We're just friends who do things and I am relaxed and happy and mature and I'm not some fickle girl! 
Help! What do guys think/ think I should do? X 
By the way, i live in the UK and the legal age is 16 for consent so that's not an issue xx