Why isn't sex very pleasurable?

I'm a 17 year old male and I have had sex for the first time with my girlfriend who I feel is my soul mate. I find her very attractive and she really turns me on. I couldn't keep a steady erection until i knew she loved me, which means I feel emotionally attached to her. We're very passionate with each other during foreplay and sex. However, when we do have sex, I give her multiple orgasms and tells me she feels fantastic (Not to toot my own horn), but yet I don't feel very pleasured. We've had sex 3 times and the first 2 I only felt a little pleasure. The 3rd time i felt more, but still not much. She's getting self-conscious because she has yet to make me orgasm, and each session lasted about 30-45 min. We have decided to take a break from sex and I want to know why I don't feel the pleasure every man has been talking about because I don't want my girlfriend to feel like she can't make me feel good. She doesn't know I feel like this. Please help