Red bumps on my penis?

Me and my girlfriend had oral sex. Then I noticed a couple hours later the base of my penis was red. I thought that it may have been from my razor and that I got razor burn since I shaved the day before and before she came over the next day. I can't remember if I shaved the same spot before she came over. It does not itch. The only time it irritates is when I touch it. But if I leave it alone there is no irritation. I trim my pubes, but I shave the hairs around and up my penis.