Losing Weight During The Winter?

I am 17 and weigh about 145, up from 130. I go to school so I don't have a lot of time for exercise, I was wondering, what are some good exercises I can do that won't take me hours to preform? I walked for a few months and got down to 115 and stayed at that weight for a few months before creeping back to... show more I am 17 and weigh about 145, up from 130. I go to school so I don't have a lot of time for exercise, I was wondering, what are some good exercises I can do that won't take me hours to preform? I walked for a few months and got down to 115 and stayed at that weight for a few months before creeping back to 130, but it's winter now and way to cold and slushy for me to go walking. So what can I do to make myself healthier? I'm not so much concerned about weight as I am about my health, I know I don't get nearly enough exercise. I hated the gym and wanted to strangle myself. So what can I do without having to buy special equipment? Anything else I should do?
Update: I wear a size 5/6 Jeans, though I don't know if that matters any. And I'm not like, squeezed into them or anything either.
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