Should I go to the ER?

For the past week I have been having brown spotting with little clots and stringy things. I got an ultrasound last Wednesday and the baby showed a heartbeat of 114, but I don't know I just have a bad feeling in my gut. I feel like I'm overreacting, but I am very worried. I called a nurse line and they said it was normal, but it's a good amount of spotting. Not enough to cover a pad, but enough to produce about a 3 quarter size spot on my underwear.