When to retake a pregnancy test?

So, I took a pregnancy test on Friday, 6th and it was negative. After feeling quite symptomatic for early pregnancy signs, ie nausea, lethargy, nasal edema, I retook a test on Wed, May 11. It was positive. Then on Friday, May 13, I started what seemed like a normal period. So I am wondering, when do I retake a pregnancy test? Unfortunately, I won't have health insurance until June 1. So going to a doctor is out of the question at this time. Could I have gotten a false positive?