Help!!!

Hey ladies, I'm so confused. So for starters my period is usually regular, might be off a day or so, but last month I had a "spotty" period it didn't even call for a tampon l, just put a pantyliner on and was fine all week. (Which isn't normal whatsoever as my periods are very heavy). And as of today I'm 7 days late/21dpo. I took a hpt at 5 days late and was negative, took two more this morning and still negative. Idk what's going on with me. My SO and I have been ttc for 2 years and I'm really hoping my levels are still just to weak to show on a test but I'm not sure. What do you guys think?