Has anyone had a false positive on a First Response or had a BFN, BFP, BFN and still got their BFP?

So, as the title suggests, I have been testing with FRES and getting BFNS, then yesterday at work I felt dizzy and rubbish and went home at lunch and tested with zero hold wee and got a BFP. Then later that evening and again this morning at 13dpo, BFN again.

I thought it was rare to get a false positive, but surely a chemical PG wouldn't appear and then go again so quickly?

Anyone else had a similar experience? and then gone on to actually be PG? AF isn't due for 2 more days.