Help!!!!

So I took the bottom test last night and it has a super faint line. I took the top test first thing this morning, after two minutes same thing, super faint line, but after like 20 minuets it was way darker. I’m just worried that maybe it’s invalid? My doctor’s nurse said if you wait too long to read it, it can give a false positive. I’m so confused, because I have missed three periods now and they have no idea why. The nurse said they just need to kick start my period again but I don’t want to if there is a chance in pregnant!