I lost 70 lbs in ~18 months but now have stretch marks on my sides of my waist when i didn't while even rapidly gaining this weight before, but now that i've lost the weight consistently slowly. how can i treat this?

Scars & VitaminE: Life holds no guarantees as we know, but vitamin e oil placed directly on the scar regularly can help to fade or remove the scar. You can get a bottle of it in the drug store. It's inexpensive and worth a try; just be patient. More importantly, please get a consult w/a plastic surgeon or dermatologist to get their input. Congrats on the weight loss. Peace and good health.

Surgery: There are creams to help bleach out any discoloration. Often, the best treatment is surgery to remove excess skin. There are some treatments by laser and ultrasound that can tighten skin, but the results are very subtle. It depends on the size and amount of lose skin.