So I'd like to put my sexual experiences up here and get some feedback. I'm 21, in good shape, I don't smoke cigarettes (although I do smoke pot now and then)

Masturbation:
Usually I'm a once-a-day kind of guy, sometimes twice. However, when I've had sex and been unable to hold an erection, it made me think that perhaps I masturbate too much, or that porn has desensitized me to normal intercourse...

girl A: 1 time- failed to keep it up (wearing a condom)

girl B: 2 times- 1st time couldn't keep it up, 2nd time came prematurely (both times I wasn't wearing a condom)

girl C: 1st time premature, 2nd time unable to climax, 3rd time premature, 4th time unable to climax (wearing a condom every time)

girl D: 1st and 2nd times unable to keep it up...the first time I restrained myself from cumming when she was going down on me, but then when I penetrated her vaginally my erection wilted. Both times her vagina seemed very dry, even though I had gone down on her beforehand. I wasn't wearing a condom either time. (she hadn't had sex for 8 months until she did it with me, it kinda seemed like her vagina was too tight)

These encounters have taken place over the span of 2 years, and it's getting to the point where I'm starting to become concerned. Especially with the last girl, because she is extremely hot, and I'd been trying to get with her for a looooong time. By not being able to perform I think I blew any chance I had with her.

I wonder if it's just that it takes a lot of sex to be able to have sex �normally,� or if I need to somehow change what I'm doing. After the last time I couldn't keep it up, I didn't feel the urge to masturbate for 8 days, but now I'm back to wanting it every day.

Any thoughts?