Do dollar store pregnancy tests actually work?

So I am 9 days late and I have been having white and sometimes clear cm as well as intermittent cramping (also vivid dreams). I have a 7 year old and my husband and I were recently married in June of 2018. We’ve been trying now for the past few months. With the odd symptoms I had I decided to grab a dollar store test to see what it would say. Instead of waiting until the morning I just took it.... immediately it turned positive. I am in complete shock. Has anyone received a false positive test from the dollar store? I am not having morning sickness like I did with my first child.... my symptoms are rather minimal as of now. I would be around 5 weeks pregnant if this is correct.