Question about loose skin

Hey, guys. I don't post on here often, but I was curious about what to do for the loose skin in my arms, legs and lower abdomen. My heaviest weight was around 256lb. I'm 5'4 and female, and over the course of 2 years, I've lost over 100lb. My goal weight was 135, but I currently weigh 133lb. I'm excited, but my body looks like an old woman. My neck is saggy, which makes me sad. I've been exercising, but my skin doesn't seem to be bouncing back like I thought it would. Any advice???