Very faint line 3 days in a row?

OK so I've taken a frer at 10 11 and 12 dpo and they are all very very faint its hard to see in pictures but I can definitely see them IRL but shouldn't they have been darker by today 12 dpo? I know there is a possibility of chemical but I'm trying to stay positive :/ has anyone had this happen and eventually get a strong BFP? I am going to wait until my AF is due on 6/9 to test again I can't take the stress. Any advice or experience would be greatly appreciated.