Pregnant but I had my period last week

I just found out that I am pregnant and I am confused because last week I had my period for 5 days. It was normal flow, it came on Tuesday and ended on Saturday. Sunday night I had very light spotting but I didn’t think too much of it. On Monday I was lightheaded whenever i’d be up for too long I felt like I would pass out. I felt like that for about 3 days so I ended up taking 3 pregnancy test yesterday and they were all positive. Has this happened to anybody? Before I got my period I was actually late for about 43 days and I took a test a week before my period came on and it was negative.