brown spotting

I'm 19weeks pregnant with mo/di twins. I had an anatamy scan yesterday and it was a little over two hours of an abdominal ultrasound so there was a lonG of pushing. I did feel a little sore after but went on with my day to work and then came home. They said everything looked great. Before going to bed I noticed I had brownish bleeding. Nothing has been red just dark brown and when I wipe it's really light brown. I am going in this morning and I am terrified something is wrong. Has anyone else experienced this?