I cannot ejaculate when I’m having sex

I’m 22(M) and I’ve had sex for about 3 times total. For some unknown reason I find it very difficult to finish when I’m with a girl, I’ve had sex for about 45-60 minutes total on my previous encounters but I can’t ejaculate and it’s quite annoying when the girls wants you to and you simply cannot. Also oral sex is quite uncomfortable, but overall erections are great I dont have an issue with it. Any advice? I used to have phimosis but fixed it with hydrocortisone 4%, is that maybe the reason why?