Thanks for query,
The curve of the pebis is due to its musculature.Anatomically it is curved .so nothing to worry for it .as sex is in our mind & not in organ.
There are four stages of sexual act .arousal,erection,ejeculation & lag period.
if you have good mental desire for sex you can have all four stages perfectly.
you also get hardness during masturbation
Just keep a gap about 2-3 days with each act.