I'm not one to do this normally if I was really worried I'd go to buy a test, but I'm really nervous right now.

I usually get my period right on time. Never misses one, I've never been late, and I guess technically I haven't missed it yet but I feel like I'm going to.
I have cramps but they don't feel like normal cramps. I'm tired all the time but that could be from working constantly. And I feel nauseous at random times.
Are these common signs of an early pregnancy or is it just stress and exhaustion from working? Is it worth taking a test?