How can you tell the difference?

I'm five weeks pregnant today( according to lmp) and I've been experiencing some period-like cramps along with some small stab like discomfort in the uterus. The pain comes and goes a few times a day for the past 3 days. It's nothing that I can't handle, but definitely noticeable. No spotting or bleeding so far. Is this normal? How can you tell the difference between you should be worried about, and something you're not? I would love some insight!!