[Danzig]

people are very much creatures of habit and of routine. you need to change yours. easier said than done? after a couple of weeks, whatever new routine you create for yourself will BE your routine.

first, go back to the doctor and tell him the vague 'diet and exercise' isn't what you need to hear. he can proscribe a proper diet, or lead you in the right direction.
walking a few minutes several times a day might be better for you rather than trying to stuff a larger block into one part of your day. don't go 0-60 right away, start doing more about 3 times a week. work your way into a daily routine.
eat on a smaller plate-sounds funny, but that way your plate is full-but it takes less to make it so. eat slowly, it takes time for your brain to realize belly is full-ever eat and about half an hour later you're miserable because you over-ate?
drink plenty of fluids, avoid alcohol, sugar and refined carbs such as bleached flour. whole grain is the way to go. have clear soup such as chicken or vegetable broth as an appetizer. avoid sodas and sweets. there are a lot of sugar-free foods out there, they're very good. as for fat free-avoid, as the fat is replaced with sugar. also, your body should get a minimum of 20g of fat a day. also, avoid trans fats at all costs! they are incredibly bad for you.
also, eat five smaller meals a day. always eat a light breakfast. and of course, if and when you eat something you shouldn't, don't just quit. you will have moments of weakness. don't chalk it up as a complete failure and give up.