5 weeks and been spotting

Hey! So I'm just looking for insight from you ladies! I just found out last Saturday that I am pregnant. Yay! But... I've had brown spotting the whole time and sometimes it even looks like a dark blood. It's never heavy enough to get in my underwear but is always there when I wipe. I've had a few light cramps every other day but nothing bad at all. Should I be concerned? My doctor says it could be normal and I go for an ultrasound on May 3rd. Help!