Can’t have an orgasm anymore

I don’t know why, but lately I’ve had some difficulty in reaching an orgasm with my SO. He’s usually reeeeally good, and most of the times he can make me cum even three or four times in a row, but during the past few weeks it’s been kinda weird. I still enjoy it very much, and even though I feel like I’m getting there for like five-ten minutes, I never do. What do you think it could be?