I am freaking out!

My period was supposed to come on Tuesday and it didn't. I took a test Wednesday and it was negative. Friday came along and still no period so I took two more tests. Both came back positive with faint lines. I had my husband confirm to make sure I wasn't mistaken. I'm ecstatic because we just had a miscarriage in April. Today is Saturday and it seems that period is on. How is this possible? What should I do? Am I misscarring again?