Pain during sex

So me and my boyfriend have been together for about 8 months now and have been having sex since the first month of dating pretty much... and it’s always been very comfortable ... but recently I don’t know what’s going on with me but when we have sex it’s just so painful.. to the point where if he even instigates sex I just say no ... my bestie thinks it’s psychological cause we’ve been having a few problems lately what do you think?