How do you reduce the size of your stomach?!

You eat less. The stomach is a muscle, capable of shrinking and expanding.

If you eat every couple of hours, (little snacks like an apple or a yoghurt - something of that size) you will stop being hungry after a couple of days and your gut will shrink.

I've been taking medication for months now (pain meds) that makes me not want to eat, so I've been forcing myself to eat just a little bit every couple of hours. Now if I go somewhere and they put a normal sized plate in front of me, there is NO WAY I could eat that much at once. I shrunk my gut!

P.S. - just make sure that what you eat is healthy, otherwise you may get sick

Maybe you could try fasting (not eating) for a day. Just drink a lot of water and juices too if you like. It will shrink your belly, wash out anything making you bloat up and clean our your intestines. When you start eating again, lay off the sugars, breads, salt. Eat slowly, and you should find yourself feeling fuller sooner (which means less stomach stretching).