Should I worry?

For the 2nd time this pregnancy I went to the bathroom and there was blood when I wiped after peeing. It wasn't too much but it was red and not pink like before. I don't have any cramping or anything I was just going for my morning per. Should I worry? Or only worry if it continues and comes with cramping? I'm 18 weeks
Also, I just had my u/s appointment Monday and everything was fine.