20 days late still getting a BFN?

Okay ladies I need some help as stated above my AF is 20 days late. I’ve never been more than 10 days late before or skipped a period. I’m having some symptoms but I gave up trying to spot symptoms because I never can tell what’s my period or not. The only one that’s really sticking out to me is I’ve woken up around 3 am sick as a dog for the last three nights then I go back to sleep and I’m fine the next day. Anyway I was wondering if anyone has ever been this late and it took them a while to get a positive test?? My dr said they won’t see me til I get a positive or miss 3 periods. I’ve been talking to a friend and she said it took her a whole month to get the BfP. And as a side note I’ve tried every brand test I can get my hands on. This would be my first time being pregnant so I have no idea what I’m doing or looking for and I don’t want to ask all my family and friends because I don’t want to get any hopes up.. thanks in advance!