Trouble orgasming (every woman's problem)

Michelle
I have never been able to orgasm atleast that I know of. I have had sex with my SO for over a year now and have been sexually active in the past. The sex is great, yet he isn't able to last nearly as long as I'd like. His fingering skills are superb thought.
Problem is I'm not even able to orgasm by myself either. I have a vibrator (not couples sadly... Saving for that bad boy). It stimulates the clit with the "bunny ears" and also will go in 3 inches. It vibrates with 3 levels of intensity and then a small variety of different pulses. 
Especially with my little toy I feel like I'm doing an ab work out that never ends and my legs shake sometimes. Which seems like good signs for an orgasm.... Yet I'm never able to relieve that tension. Eventually I have to stop because I feel like I've done 1000 crunches. How can I just freaking let it go and orgasm???????