Weird problems when having sex

Hi everyone, I am 20 years old and a fit guy.

I had a strange problem when having sex which is that at first i will go very hard during foreplay. But then when the motion stops for a while (such as getting a condom etc), and which my dick have enough time to calm down and go flaccid, it is very hard toget back up again even i fell horny as hell. But if i manage to get it up, It will ejaculate before reaching full erect( around 60% erect usually). I wonder if anyone here have similar experience before and any advices for me?

In my opinion, that's the dreaded "window of anxiety". I had that same problem 20 years ago.

Have your partner put the condom on your Johnson, and try to stay in the moment before you penetrate him/her by using your senses. And then do Kegel exercises to work on ejaculating too quickly.