I wouldn't worry about it at all... unless you have reason to beleive you might be contracting a std. I'm sure if you ask any girl she'd tell you that dry shaving or shaving without enough foam can cause little red bumps on ones skin. As you know, I'm sure, the skin on a penis is very sensitive and using a dull razor might also be an issue. Try vit E or a very gentle shaving cream if you contiune to shave....
and i havent had sex with anyone but my partner in the last 3 years