Two lines but then one

I've had period/ early stage pregnancy symptoms such as the typical sore breasts gas cramps back ache dizziness occasionally, feeling tired mood changes. I came off the depo jab four months ago and had a little spotting a week after nothing since so did a test today and it showed two lines then the positive went completely round when the time limit finished. I don't know what to think of it as I've never had this problem