Becks your chart is looking great, you should test again.
I've heard of people getting negative after positive and then positive again and it's put down to either too diluted urine or vanishing twin.
I don't know about you but I always get a temp drop on my chart before AF shows up.
I know it's really tough to see a negative after a positive but you have a longer than usual LP, your temps are going up, you are not getting your usual spotting pattern and have sore boobs. These are all very positive signs.
I would test again with a FRER after withholding liquids for a couple of hours. I'm really hoping you have a good outcome

