Day 48 & feeling sick

It's been 48 days since last intercourse. Past month I've been feeling sick, upset stomach after I eat, and nauscious. I've been under a lot of stress past 5 months.. I did get my period last month & took home pregnancy test  5 days ago (it was negative) is there any chance I could be pregnant? Or is this something more serious like gastritis, or an ulcer?