CD 70 no af, bfn

Lauren
Hi guys I'm new, just looking for a bit of advice really as title says I'm on cd 70 no af,  no spotting and 3 bfn went to dr and had blood test to see if that showed anything- it didn't. got an internal scan on 7/3 been off bc 10 months and cycles been anything from 30 days to 42 previously and I've been under no stress that I'm aware of. What do you think? 
Hope I've done this correctly guys, sorry if I haven't!