Confused - 2 positive tests, 1 negative

Hi ladies. Just wondering if anyone has experienced the same as me. I did an at home test last Wednesday, it was negative, another one Friday morning, it was positive, and Monday evening and it was positive too. My period is now a week late.  
I went to the doctor this morning and got a negative :( he said it could be the concentration of the sample or that I'm super early. He sent me for blood tests so I'm waiting to hear back. 
Has anyone else had this? It's totally confusing me and I'm crossing my fingers that we are pregnant.