Fellatio

So my boyfriend was my first sex partner, we've broken up a few times since then so I know I haven't been as passionate about doing this to anyone but him. I get really into head with him, but all these years he has never came from head from me. I know he has from others he's told me, so it makes me wonder what I'm doing wrong. He doesn't make me feel bad about it, he asks for it all the time, and he gets really into it too. I've watched porn etc, and it just won't happen. Any suggestions?