Hello and welcome to eHealth Forum!

The symptoms ‘every time I reach an orgasm I tense up inside it feels like, I’ve tried everything to stop myself and cant and I lose my orgasm’ only shows that you are very tense for some reason. You re comparing the type of orgasm you had earlier with what you have now. The feelings and what you go through in an orgasm may differ from time to time, may differ with the method used for masturbation and also there will be difference between real sex and masturbation.

The trick is to relax, such as take a relaxed bath or listen to music etc before the act. As a practice normally try deep breathing exercises to remain relaxed.
If the problem persists consult a doctor. Hope this helps. Take care!