Irritation in vagina when I finished my period and there was some brown blood as well

I just got off my period and I like to dry hump my pillow .... I went to the bathroom and when I peed it was a little uncomfortable because it kind of burned and there was brown blood .... what does this mean .. I keep getting this Thought that I’m pregnant .. but I don’t have penis to vagina sex .. I only hump pillows for my pleasure