Blood drawn before implantation?

I had blood drawn on Monday which would put me at like 7/8dpo. I had brown spotting Christmas morning that I believe is implantation bleeding given that I’ve not had anymore spotting or bleeding and no pain or cramping. Got a faint positive this morning. Blood results from Monday were negative and my progesterone was 2.5. Is this to be expected before implantation?!? I’ve read that progesterone should be 2 or

More before implantation and then rise 1-2 ml everyday after. Any insight is helpful!! I’m not due for my period until Friday and I would be 3 weeks 4 days today.