Af 20 days late Bfp then two days latet Bfn?

Today my Af is 20 days late ... Friday 18 days late I took a Clear blue easy and there was a faint Bfp so I rushed out and got a equate first response hpt (if a line shows positive no line negative) and it was positive:) I was ecstatic but then this morning I took the two left of each brand and they were bfn! Any advice? My period is due again in 6 days if Af doesn't show it willl be my second one missed. I am a regular 26 day cycler :) I've never missed Af before.