This definitely sounds psychological. A lot of people seem to get their 'sexual esteem' based on how many orgasms they can give, which is a terrible way to judge themselves as orgasms aren't everything: it should feel good before you get to orgasm. Also, the psychological block (which I suffer from too) of knowing that someone is trying to make you cum, and the potential that their self esteem is riding on it, well, is just too much to think about and... makes you not cum! And the more you want to cum and panic about it not happening already, the less turned on you are. And the more stressed you get. And so on.
I reckon the psychology goes deeper than that so have a think about that - when did you first become interested in sex? was it ever forced upon you (even if it's just boys playing kiss chase in the playground), so that you associate sex with being unhappy or shutting off emotions? It could be a reflex where your mind starts enjoying sexual ideas until they become real, and then it kicks into defense mode. What you want to do is break down that wall.
Whether or not it goes as deep as that or is simply stress, try having a rule with your boyfriend that you're not allowed to cum. It's a trick that works in MANY cases, but whatever happens make sure it's clear that he has to follow through with this - no matter how horny you are. If you don't believe he won't let you cum, the psychology of it won't work. Of course after a few sessions of this you might be able to break that barrier and revert into that mindset of really wanting to cum, so much that you don't care whether you're being good/bad at sex, or pleasing your partner, or not. And then you will orgasm.
Worked for me, and many others I'm friends with! ~~~