HCG did not double is early Pregnancy

Courtney

I went in for my first HCG 3 days before my period was due (Thursday) number came back 36.

Second test was done the day after my period was due (Monday) and numbers came back at 68. So did not double in 4 days.

I have had no bleeding and tiny little cramps that don’t last more than a few seconds. Boobs still hurt and I feel nauseous when I wake or have not eaten anything.

I have a 3rd test booked for today (Wednesday)

Has anybody had this and had a healthy pregnancy or and I definitely going to have a misscarage?