T & P your way, and I would say yes it is possible you are only 4-5 weeks. I got my 1st BFP on 11/12 after having a BFN on a HPT on 11/5 and a BFN at the Dr's on 11/7. My LMP was 9/20. I had been having 42 day cycles, so in theory should have had AF arrive on 11/1. When I went to my Dr to confim on 11/13 I was told that I was probably 7-8 weeks already (if this were the case why did it not show up the week before). At any rate the following week I had some bleeding and the OB suggested I go to the ER. At that point they did blood work and an U/S and I was measuring 5w3d at the time (which according to my PCP I should have been 8-9 weeks). I went to my 1st OB appt on 11/29 and they did another U/S and there was a HB and I measured in my 6th week. All to say that I am 3-4 weeks behind what I would be going off of my LMP.
I have seen some women on here test positive as earlier as in their 3rd week.
Take it day by day and I'd wait until after you get your bloodwork from Thurs back. GL