Difficulty Orgasming

I've never orgasmed from sex with a guy, only through masturbation. I've had multiple partners but sex has never been great for me. I LOVE foreplay and oral; through oral I've almost reached it but haven't.
 I dont have sex frequently (could I be too tight?), maybe three times a year. I just dont know why it doesn't feel good or why I can't reach orgasm. It's uncomfortable and not pleasing. Any advice?