Keto and amenorrhea

Dear ladies, I need some help! I was following keto diet for almost a month(ate like 20-50g carbs per day). And now I dont have my period.

12dpo I had some cramping and brown spotting, very minimal, and since then nothing. I took htp-bfn, today I will go to make a blood test.

I dont believe that keto for 3,5 weeks is the reason. Maybe its super late implantation, it could happen 6-12 days after ovulation.

Also I dont have any other symptoms, just sensitive nipples.