Just because first responses day they CAN detect pregnancy 6 days before you're due it doesn't mean they WILL. If you look at the stats, they'll only detect donating like 70% of positives that early if I remember rightly. I know its hard, bit you're best of waiting until you're due at least. Good luck!
I didn't get a bfp until a week after my period was due, I used every test under the sun including FR and they were all negative then a week after I did a cb digital and there was the pregnant 1-2 weeks. I've worked out that its cos I ovulated later than I thought in my cycle so bear that in mind. To me FR say they can detect but it didn't for me! Fingers crossed xxx
I think there's a big issue with these early tests of sending you a bit mental! I know they can sometimes detect very early but as pickle says there's no guarantee they will. Even if you get a BFP this early, you'll be on tenterhooks waiting to see if its a chemical pregnancy. I got my BFP two days before AF was due and those were two very long days! Your best bet is to sit on your hands and test when AF is due!
First pregnancy I wasn't sure of dates, but had a neg test first before I had a pos. Counting back after scan, I reckon that pos wasn't until after AF due, so maybe 16 dpo. This time round, I tested every few days from 5 weeks post AF and only just got a pos at around 7 weeks pg. It happens to loads of people.