Dissapearing BFP *update*

I took a frer this morning at 10dpo and I set the timer for 3 minutes and walked away. When the timer went off I looked at the test and I had a faint line! I was so excited! But when I looked at it 15 minutes later the line had completely disappeared. So I am sad and wondering what is up. Anyone have similar experiences and what were your results?

UPDATE: I think yesterday's test was just too early. I tested this morning (11dpo) with FMU on a frer and a cheapie and both have a positive! Looks like baby #3 is on the way!!!