I'm 5 weeks and 2 days pregnant and now I'm bleeding.

Hi, I'm 5 weeks and 2 days pregnant now and since this morning I've been spotting a little. I had an ultrasound this morning and everything was fine, but now I'm bleeding more. I called the doctor and she said it can happen because bleeding doesn't just stop on its own, but if I get cramps, a lot of bleeding, or a high fever, I should come back. I'm so anxious—I haven't been pregnant for 5 years and now finally again. I really hope the bleeding stops.