SEX HELP PLEASE

Okay so this is so embarrassing. But seriously. I'm 20 years old, and I have had sex numerous times, and I have NEVER been able to orgasm during sex. Ever. EVEN when the guy was doing exactly what I wanted and what feels good to me!! I don't understand why. I am a little self conscious about my body, so I figured maybe it's because I'm not letting myself fully let go and relax because I'm too worried about what he thinks I look like at the time or whatever. How do I get past this??? I want to enjoy myself and him too! It's been a long time since I've had sex with anyone. And I really want it to go well with this guy because he treats me so kindly. I just don't want to ruin it for both of us!