Fainting Positive First Response Test

My fiance and I are trying for baby #1. I started my first round of clomid end of last month, I'm 4 days from AF. I started light pink spotting yesterday just when using the restroom so I decided to take a test first thing this morning. As the test starts to read the pregnancy line shows immediately slightly pink then the control line, but within seconds the pregnancy line disappears. I was so excited, tears started, but then my heart was crushed! Has anyone else had this happen? Did you end up being pregnant?