Positive line disappearing?!?!?

Ok so I am 2 days late and took a test (in the middle of the day I know but I was anxious) anyways so I took it let it sit it showed up positive so I picked it up to show my husband and when I made it to the other room it was gone just completely gone and it was a dark line. I didn't imagine it even though that's how I feel since it just disappeared I've never had this happen before this would be kid #3. Has anyone else ever had this issue? Going to take another one in the morning but until then.....

Thanks for any input!