Dark brown spotting

So at 10 weeks I had brown spotting after sex that stopped after a few days. I called my doctor and she said it was completely normal after sex and not to worry unless it turns red and is enough to soak through a pad. Well, I'm 13 weeks now and have been spotting for a few days. We haven't had sex but did "fool around" a few days before the spotting started (idk if N orgasm can cause spotting) . I know the doc says I have nothing to worry about but is random spotting normal?? Should I go to the ER?