22 weeks and spotting after ultrasound?

Hi ladies. So I had a growth scan today with a trans-vaginal ultra sound to measure my cervix. Everything looked great. Both boys are just over 1 lb and my cervix is long at over 4 mm. Since the ultrasound I've been a little crampy and started spotting. It's not much, but since I haven't had any issues at all, I'm a little freaked out. I spoke to my OB who assured me it's nothing to worry about but I'd love to hear from someone else who went through this too.