I have been ttc for about 6 months and I have been using OPK for the last 4 and they ALWAYS give only a faint test line - even when I've been testing 3 times a day (close to when I know I'll be ovulating). Everyone says a faint OPK is negative - but what if thats all you ever get? Whats going on? I have a regular cycle 24-27 days on average with luteal phase around 13 days. I've had blood tests that definitely show I'm ovulating so why the faint line??

Any answers would be much appreciated.