Why??

So I've been dating my boyfriend for about 6 months now and he's my first everything. I expected not to cum the first few times but I've only been able to cum once out of all the times we had sex (we've had sex a lot lol). I don't really even cum during oral. Don't get me wrong everything we do feels great and I love it but it's so hard for me to get off. Am I the only one? And how can I get myself to actually climax?