How long will it take for my legs to stop jiggling?

I'm almost 5'8 and I'm 142 pounds I'm not fat or anything...but i cant walk without my legs jiggling like crazy...like a ripple effect when i jump or run so i don't really wear shorts or bathing suits often. since it's summer i want to workout like crazy to get my body in shape for when school starts. as of right now i have to months...will i have enough time to get a sexy toned body? how long does it usually take?