Getting myself off

I've always felt embarrassed in writing this on here. So here it goes because it's normal to pleasure yourself.

I've been getting myself off with a vibrator for a few years, I like the sensation of the vibrations against my clit. I've made myself come a few times in the past. I feel like I'm getting close to coming like I feel it ready but I just never seem to be able to, I feel like I can't relax myself enough. The same has happened when a guy is getting me off and I get the similar sensation but I can't seem to relax enough. So I basically don't think I'm able to come... Any advice on how to let go and just relax please? (Also I'm on some antidepressants which I may think is the cause but who knows, I've come off one of them and still taking one set a low dosage which I'll be off by the end of this year I hope)