Do you have 15 to 20 minutes that you could exercise daily? You really don't need all that much time. You could walk, run or use an in-house stepper. Running hard for 20 minutes is about 2 miles, for most people that are just recreational runners.
For weight lifting, you can get some of those hand-held weights, at one of the sports-type stores. I have some that range from 3lbs. to 40lbs. each. Hand-held weights are great because they don't take up a lot of space, and you can do them in front of the TV.
After a hard day's work or a tough time at school, a workout can make you feel better. It relieves a lot of stress. I know it helps me sleep better too. So some exercise could actually help you.
Follow a nutritious diet too, consuming natural non-processed foods as much as possible.