Hi Nicrach

The most sensitive you can get are 10 miu. Google it and you should find some. First Response/Clearblue both v good brands but apparently the ones you get over the counter like FR and CB measure 25 miu or over and more then likely nearer 50 miu and both claim to be able to detect as early as 4 days before AF.

The 10 mius are the most sensitive as they are ultra early preggo tests so I agree with MSB26 - get those over the net, probably won't be a brand you've heard of but I got a BFP around 8DPO and then to be sure follow on with a brand name you trust.

Good luck - fingers crossed.