I'm sorry about the bfn...
Listen, you really should see a OBGYN. If you aren't having a period, you probably aren't ovulating. I know, because I am in the same boat. I had hormone testing the day I went off of the pill (a few months ago) and I am perfectly healthy, but I don't get (and have never had!) regular periods. I'm not overweight myself, so that line your GP gave you is a load of rubbish, as far as I'm concerned.
Your OBGYN can put you on a drug called clomid which will make you ovulate. I've heard that it works so well, you can chart your ovulation time down to the day!
I'll be asking my OBGYN to put me on it at my appt on Tuesday.
Good luck!