I’ve been randomly spotting for a week!! Help!!

So it’s a week before I’m supposed to start my period (news flash, I never get it on time) and I get a really terrible stomach ache followed by nausea and vomiting. At first I thought it’s probably a stomach virus. This lasted for about 2 days. The second day I started spotting dark brown.... the rest of the week I felt fine but continued spotting. Some days really heavy and some days barely anything. Most of it was dark brown but occasionally some dark red (especially when wiping). I’m super confused and a little worried. FYI I had sex right after I finished my last period so.... pregnant ? Not pregnant? Miscarriage? Please help!