Tested negative at 12dpo.... no af and weird symptom

Alyssa
I counted myself out after I tested negative at 12
Dpo.  Still no period but it's not uncommon for me to be late. I would be 16 dpo at this time.
The weird thing is I'm a big walker and tennis player.  I put on about 8-10 miles per day no issue. The past three days I have been getting stitches in my side.  I'm also pretty tired.
Am I just wasting money in buying more tests? Sound like anything for anyone?