Please help with pregnancy test?

I had unprotected 2 weeks ago, and decided to take a pregnancy test every week. last week it says I wasn't pregnant and I took one last night. At first the little circle that tells you if your pregnant or not had like water ripples in it. I looked at it 10 mins later and it said I wasn't then this morning it said I was. I'm really worried am I pregnant or not. What are the odds of a false pregnancy test??