need so advice and prayers

Hi ladies, I am in my second FET 8dpt5dt and I have been poas since day 5. I have a BFP and have been testing since and it has been getting darker. Today I poas in the am and then around 1 I decided to poas again and it was a bit lighter than my fmu. I'm scared that maybe it might mean it's not sticking? My other days I've poas in afternoon and it was darker than my fmu. Can anyone help or no why today it might be lighter than my fmu?