HELP!! He Keeps Hitting My Cervix!!

So I'm really flexible, and my boyfriend LOVES it, however lately, when we're having sex and my legs are on his shoulders, it hurts really bad. I think it's because he's hitting my cervix? We've tried a lot of different things, he goes slow and it's plenty lubricated and he lets me get comfortable and is really gentle but it still hurts so bad! He really enjoys the position, and I always feel bad telling him it's too much and to stop, so is there anything I can do to stop the pain??