Line progression


Okay someone give it to me straight. Is line progression a real thing? I found out I was pregnant on the 1st and got a very faint line. On the 2nd, I took another test and it was slightly darker. I waited 3 days and took another test yesterday, 5th, and it was not darker. I freaked out and called my ob today to request blood work to see what was going on and she said not to worry about the darkness, that if there’s a line, I’m pregnant. But I see everyone posting their line progression and I can’t help but worry. So someone please tell me, is there something to worry about?!