Dear Mrs C,
Whilst you shouldn't attempt any strenuous exercise after tment, and esp in 2ww, I think running at other times is OK. I started running in Feb (literally couldn't get to the end of my road then, now can run for 30 mins without stopping!!!) I would advise a gentle programme of run- walk-run until you get fitter, as it's very hard! If you check out www.raceforlife.co.uk they have a great 6 wk beginners programme that works really well.
I also go to the gym. I think it's a case of bring sensible. If you are interested in losing weight, running is the best way, in conjuction with a healthy diet. I would never put myself or my efforts in ttc at risk by overdoing it, but for me at the moment whilst waiting for an HSG appointment, sometimes running or gyming it is the only thing that keeps me sane!!!
Good luck.
xxx