Sexual Performance Anxiety

I am friends with a girl who I really love but she is all over the board with her feelings about me. Anyway, before I met her I was a virgin. We have been off and on for about 3 months. I'm 37, I waited because, actually, I avoided sex because I was embarrassed because I only have one testicle. I thought I would be looked on as a freak so I just closed down. That, plus I have OCD really bad so I just naturally withdrew from the dating scene. I lost my testicle when I was 17, it twisted, cut off circulation. Anyway, we have gotten together and I know how to "get her off" but when it comes down to penetration I get extremely nervous and have only been able to perform one time. I get so nervous about getting a satisfying erection. She tried giving me a "blow job" last night but I was only half aroused down there. In my mind I was so turned on, but I was also so nervous and instead of letting go and enjoying it, I sat there in a panic. I thought, "get hard, get porn star hard, and cum!" Needless to say, I dropped the ball big time. She has really been understanding but enough is enough. How do I end this problem once and for all? Also, I went on Cialis for a short while, got massive erections but even then, we tried only one time while I was on it and I lost my erection. What's crazy is I can masturbate anytime, no problem. It's just if she is around.......I get so nervous. I really love her. I want to marry her but I don't feel like a man. I want to add that I live in Kansas and I don't have any money, I just got desperate and saw your site. I have lost all joy. I am so burdened and hurt and embarrassed. Life sucks right now. Also, again, I have OCD. I know that is a huge factor in all of this. My OCD is going crazy and even though I can masturbate at will I don't remember the last time I woke up with an erection. I masturbated four times yesterday, just to test things but why do I not wake up aroused anymore and why am I not getting hard at the mere site of seeing her nude? She is an angel, so beautiful. Am I ok? Is there something wrong physically or is it in my head? Also, I should add that I used to be on medication but am not currently on it. I went off my Paxil a month ago thinking that it might have been the problem.