can't orgasm

I'm 18 and have been in four relationships, three being sexual, the first lasted two years, the second was a few months, and my current is going on a year, i am a very sexual person and very vocal about what I want and how things make me feel in bed, I crave reaching climax but I never have and I'm afriad I just can't but I wonder if it's just because I've only been with three inexperienced guys, also I have tried masterbation a bunch and have never orgasmed from that either.... I don't have a vibrator or anything, would that help? And is it normal to never orgasm even though you're sexually active???