While at work..

While I'm at work (I'm a waitress) I've noticed that when I wipe after I pee there will be light pink blood (only once a day) I'll wait 30 mins and go back to the bathroom and there won't be any blood at all. It's done this twice and being a ftm it freaked me out. 
Everybody is telling me it's normal... is it? What's causing it?