Why did I lose erection during sexual intercourse with a prostitute?

On my 24th birthday I went to a legal prostitution facility and picked out the best looking girl to have sex. I didn't expect it to last long so I paid for half an hour, which cost me six hundred dollars. I haven't had sex with a woman since I was 16 years old so I wanted more experience before starting a relationship with a girl I like. When the prostitute gave me oral sex it was an instant erection and she asked me if I wanted to come right then. But I wanted to try straight sex with her to learn positions and get better at sex. So I helped her masturbate until she was ready. She used a lot of lube with toys. When she got me ready with oral again, I wasn't as hard as before but good enough to get a condom on. I was shocked at how loose her vagina was and I couldn't get complete erection which made it hard for me to keep my penis inside. I hardly felt anything because she was so loose. My penis isn't that big but it is 5 and a half to 6 inches long when rock hard. We tried several positions and after the third she took the condom off and gave me oral again. She used lots of lube with a hand job but I just couldn't get more than half an erection. I knew I could get really hard if I could have held her head down while she gave me oral but she wouldn't let me. After 28 minutes I finally got pretty hard again almost to the point of an orgasm but the time was up and she wanted another three hundred for another half hour. As I didn't have the money so I just left. I can't stop thinking about what was wrong with me. I found her body so attractive. The sex just seemed really fake and I sort of was turned off by that fact. I am frustrated because I went to her to get sexual confidence and now I can't stop thinking about it when I go to sleep. I know I could have done it right if she wouldn't have used so much lube or if I had tried more sexually appealing positions to me. I can't stop thinking about it. Only if I should have told her to keep on with oral sex when I was rock hard, I would have come. I know that I won't see her again but my pride is hurt from this experience. When I masturbate to porn I get so hard that my penis touches my belly. When I wake up in the morning it is still hard at times. Maybe I am just not sexually attracted to prostitutes and need a woman I love to have sex with. Have you ever heard of this happening before or should I see a doctor? The prostitute asked me whether I was on cocaine but I was not. But I was hooked to crystal meth for 4 years and I would masturbate a lot on it for incredible orgasms. I have been off it for 9 months now. Did this affect anything? I still can masturbate easily in 10 minutes.