Hi, I used to masturbate once a day or once in two days, but then I started to do it twice a day for two days. On the second time of the second day, i had erection initially and then lost erection and ejaculated. I didn't pay attention to it, but for the next masturbation, i couldn't have an erection then ejaculated. Since then, it's hard to gain erection and i feel itchy or irritated under the tip of my penis where it's sensitive to arousal. What could the problem be?