How long is too long to check for a test result?

I look the top test early this morning (first pee of the day!) and it was blue but just like a blur in the positive spot. So I left it and went about my business, went to work and about 10 hours later looked at it again and saw the faint blue line. So when I saw that I took another one. And the line is even more faint but can be seen. Has anyone ever experienced this before? We had a miscarriage two years ago and haven’t been able to get pregnant again. I don’t want to get my hopes up until I know for sure, just looking to see what everyone thinks!! Thanks so much.