How early can you test?

Lisa
How early can we take a test? AF is due 26/01/16. After 3 miscarriage I am desperate for a baby. Me and my husband have been together 10 years and my first two miscarriage were 8 years ago my last one was November just gone. I am now under investigation and after having my scan to check my uterus and ovaries last Tuesday the lady scanning me was able to tell me that I had just ovulate which is the correct day according to this app. So having had intercourse the day before and two days prior I am really hoping it has worked this month and I can have my sticky baby. I am being so impatient and want to know now. :( sorry to go on. Xx