What’s going on ??

I am 12 days late , I take a test and all of them are negative. I feel sick and I get nauseous in the morning , I get really tired during the school day . There is a chance I could be pregnant ?? I had sex in July after I got off my period and I haven’t had my period since . I took a test every week , also there was a faint line on one but I took another and it was negative.