If nothing else changes,but spotting continues after the next period go see a gyn. It could be absolutely nothing or it could be hormone caused. Stress also causes odd things to happen to your periods. Here's a question to consider, any chance of pregnancy? It doesn't happen often, but some women have periods the 1st trimester. My mom had periods every month of her 1st pregnancy (that's rare)! Don't freak if there's no chance, but think on it anyways.
As for the weight loss. We all get to plateaus with losing pounds. Try increasing your excercise slightly so that you are losing again. Sometimes it's just that calories taken in are equaling calories being burned off. A little more activity will tip the balance again!!