What could it be?

Kia
Anybody ever been almost a week late, had BFN, and pregnant? So, AF was due 8/9 and I'm now 4 days late. Took tests aug 9 & 10th and they were negative so I'm trying to put it in my head that I'm not pregnant and my cycles are going back to being irregular. Got pregnant in March and had a mc at 5-6 weeks. Been trying since then and my periods have been pretty regular since the mc. The only thing I have done differently is add prenatal vitamins to the process this cycle. Could the vitamins be the reason I'm late? I feel crazy just asking but that's the only thing I've added to the process. In the back of my head I know the vitamins probably aren't the reason and if I don't start next week I'm thinking about going to the doctor to see what's going on because I'm scared and feel if I go and buy another test it'll just be for nothing (BFN 😑). I've been so emotional that I cried the other night about the fact I got BFNs and then it turned in to me crying about the mc. My SO thinks I'm pregnant. I just hope he's right 😞