Period ended a week ago, positive test

Has anyone ever had their period and then less than a week after it was done test positive? I had a full out heavy period and then had sex like 5 days ago. Today I had spotting and it threw me off because I haven't had my period irregularly in years. Took 3 different tests and tested positive on all of them. Should I be worried if I am lightly bleeding right now? I don't know how I could have gotten pregnant 5 days ago and already have a positive, so I had to have gotten pregnant in March. Has anyone had anything like this happen to them before?