AM I able to get an accurate reading on a pregnancy test at...?

I am 12/13 DPO and have a doctors appt and I want to know if at 12/13DPO its is possible to get an accurate BFP or BFN. I tried to hold out on first morning urine, but I had to go sooo bad...any answers would help thanks! P.S. I do have a few out of the norm symptoms.