I took two couch to 5k group of local ladies last year and at the beginning of this year. They all had trouble breathing at the beginning. Something to try is breathing in twice then out in time with your footsteps (this also works well if you're asthmatic). So as you run breathe in and in again then out, in and in again then out.
If you can, as others have said, run outside. Try to run on softer surfaces such as grass in your local park as you'll be less prone to injuries than pounding the pavements.
As for food, you need to be prepared and organised. Don't buy chocolates, sweets, crisps etc from the supermarket then you'll be less tempted to eat them when you get home. Buy fruit and vegetables, cut some into pieces so you have snacks readily available. Always have water available and try drinking before you eat. Some of my ladies found my fitness pal to be useful as it made them realise they were eating more than they thought if they recorded everything.
Can you go for a walk at lunchtime rather than staying in your office? Or even set a reminder on your phone to get up every hour and stretch your legs.
Good luck with your running and weight loss. With a bit of determination you will get there.