3 positive then 2 negative test

Hey ladies, so last year had a eptopic pregnancy that resulted in emergency surgery and taking part of my left tube. So we weren't really trying to get pregnant but if it happened we would be ok with it! Well a few days ago I had all the symptoms and took a test and got a Very Faint Positive! The next few days after that I got positives and took one that said pregnant! Well this morning I took two test, one looked negative and then took another and it said not pregnant. What is going on? I should be around 5 weeks today. I've had no bleeding, but woke up this morning really dizzy and with a headache.