Ok ladies help

Af aint due until 12 days I feel real nausea wanna eat but don't eat a lot sometimes I eat a lot my back hurts head hurts my belly feels tight like im 600lbs my mood swings are crazy I had my monthly last month but it was early only 3 days not bad ( I heard u could have af and still be pregnant ) I have heartburn really bad should I take a chance and buy a test or what? But I am scared I'm going to get a pfn !!!! Just a little help please