Cracks on penis head glans (pics)

Well I'm not real sure where to start but I've been sexually active for 3 months with my girlfriend without a condom. She recently before we got together was tested and everything came back good. After we've been having sex I've paid for attention to These cracks on the glans of my penis. I've went to the doctor and he says they are nothing to worry about but I tend to let things worry me alot. I have no pain/irritation/funny colors or spots. I'm just worried that one day the cracks will get worse and like rip open. :( I am curcumcised and to be honest I cannot remember If I've had these cracks for a long time or not. I haven't been sexually active for 4 years until my current girlfriend. I'm asking on here to see if anyone knows what this is and can give some advice thanks! I cannot post links due to post limiter. I can message anyone the links for the pics.

Source: MD Health Forum - Medical Discussion Boards - April 20, 2013 Category: Consumer Health Advice Authors: Doktamaja Tags: Men's Health Source Type: forums