pregnancy tests

Mother's Day weekend...so I took a test on Sunday and it was positive. Took another the next morning and it said negative. I was bummed out but everyone was telling me to keep trying! Well I took another one just this morning when I woke up and it's negative. How can I have a false positive??? I read those are rare and that false negatives happen all the time! I think I'll wait and see if I miss my period this month! I'm so upset that was such a tease! Has this happened to anyone???