Is this an STD/STI? I'm freaking out

I've had the spot on the bottom of the shaft and right underneath the head for 3-4 days now. The spot at the bottom of the shaft I cut accidentally when shaving a little more than a week ago. After that, I thought it went away. Then the spot underneath the head showed up. I believe this could possibly be a friction blister, because I hump in my sleep and when I get morning wood, I pull my penis upwards, which could've caused friction in that area because of the belt lining area on my pants. The tiny red spots on the shaft and the spots on the right just showed up yesterday. I have been freaking out tremendously over it. I went to the doctor already and my STD/STI test results came back negative. But it looks so weird that I'm still scared. My sexual partner (female) and I are mutual to each other (as far as I know, I know that I am to her obviously.) Someone help me out here.imageimageimageimage