I would def go and see what is going on always better to be safe than sorry I always say.
so far what your describing doesn't sound like its too urgent but you should definately call your obgyn because you never know. It is true that if you had a vaginal ultrasound that this can cause bleeding. You should go to the er right away if you see blood clots and have abdominal pain. Also urgent if you fill more than 2-3 pads an hour. Sticky baby dust!!
I got a vaginal ultrasound thursday my sister said maybe its from that and I can tell I have a bladder infection