TTC ISSUES

Af was due on the 7th. I have no symptoms except lower back pain. I took a hpt the day before I missed af at 13dpo but I got a bfn. I am now 17 dpo and still no sign of af I had weird twinges below my belly button but nothing major. I was trying to wait a couple of days for af to show before I called my doctor and I definitely do not want to get my hopes up. I really don't know what to do because I don't want to buy more hpt just so they can say no 😢.  Or making an appointment and then af wants to show up. This is a nerve wrecking process 😒