I often see that my erected penis when i woke up.. is it disease? any medicine? i think i'm little mentally nervous and worrying for many things..

Normal: It's completely normal to have nighttime erections (several) and to wake up with an erection. In fact, it is a healthy sign and it is what physicians ask about since there is decreased anxiety usually overnight and with sleep, so that the patient's "true" erectile function can be identified. This is not something to worry about.

Morning erection: It's perfectly normal to wake up w/morning erections. In fact, as we get older, we worry more if we wake up w/o them, especially if we complain of erectile dysfunction & loss of libido. So don't worry about your morning erection.