I'm going through the same right now I do it for him but he doesn't push it but I feel I should because he has a high sex drive. I just find that when he spends more time on trying to get you aroused has helped me a lot it just takes some doing. Its just phases though it won't be for ever
Though you may not feel like sex, I would recommend buying your boyfriend a pocket *****- you can use it on him and they're cheap from the sex store, this may help keep him happy in the short term.
I'll often just let my boyfriend have his way as often even though I don't feel like having sex, It doesn't bother me to actually have it, I'll be bored but oh well it'll keep him happy for another day.
If you want to try increase sex drive, try some natural libido increase pills you can get them at most pharmacy's or you can try the ones they sell at the sex shop,