How long did it take to get your BFP after missed period?

I'm a week late and have pregnancy signs. Been having sore breasts for over a week now. They seem to be getting fuller/bigger. Light nausea, especially after I get up in the morning. Horrible gas. And extreme fatigue. I can sleep for 10/12hours and still be exhausted. But I've got two very faint could possibly be negative tests and the rest solid BFN's. Could my hcg just be low? I see my midwife Tuesday.