Late period? Stress? Pregnant?

I’m three weeks late. I’ve had bubbles in my stomach like air moving but no gas. My nipples are so sore and I’ve been nauseous on and off al through the day. Also have headaches but that could be job related. I’ve been testing and there looks like there could be a faint line but it’s very very faint. I work in a stressful field and this month has been hard. Do you think I’m pregnant or could it just be stress?