How cum I can't cum?

Katie
So I'm 18, been having sex for 3 years with mutltiple different people, more times than I can remember, but I have never had an orgasm before! Of course other stuff has been performed such as eating out, fingering, some cliteral action. Has anyone not been able to come EVER and has had sex with different people/tried different things? What works for those of you who can  cum?