Has anyone had a plus show up on a + and - pregnancy test less than an hour after using it?

Any stories of not being pregnant and having the plus box show up after the 10 minutes, or were you actually pregnant? I'm taking one in the morning but I'm freaking out now. I did read the instructions, just wanted to know if this is a cause for worry. First time ever using pregnancy tests to I don't know all the ins and outs yet.