20 days late, neg test, my cycles a whole damn mess.

Okay so i was without a period for like a year (wasnt on any medication/bc) until june 15th i got my period (finally) and it ended on the 23rd of june. Then i got my period again from the 24th of july until august 19th (already seen my doctor. Apparently my ovaries are fine, no signs of pcos or anything else). I was supposed to ovulate the 18th of august according to Glow (Not sure if i did. i hate ovulation tests). Now, i have no idea when im supposed to start my period again. Glow says im 20 days late now. I took a pregnancy test yesterday and it was negative. But i feel really drowsy/fatigue and groggy along with a very mild headache. Ive never felt this way before...

Has anyone been through this before a bfp? Or did you feel this way and it turned out to be nothing?