Signs of miscarriage...

I found out last Saturday I was pregnant... I went to doc Friday to confirm. He confirmed but bc I have been exclusively breastfeeding,taking mini pill and haven't had a period since dec 2015 we don't know exactly how far along I am.... so he checked me and said my uterus was small
So he is guessing I'm about 5 weeks.... I've been taking the Walmart brand test and the line isn't getting darker,yesterday when I wiped there was some pink not a lot and my belly has been really crampy... I'm going crazy ultrasound not scheduled till the 14th