Lose 20 lbs in 2 months?

Im female, 23 yo, 5 ft 2 inches, 130 lbs and i want to get down to 110 lbs in 2 months. I have a 3 month old baby that i am home with all day as a sahm, and i should mention i went from 160 to 130 and my prepregnancy weoght was 110. I take medivation for adhd which also suppresses my appitite so i have about 500 - 900 calorie deficiency a day and walk a little under 5 miles almost daily (tredmill)... i also drink a lot of water. About 2 litres. I cant seem to lose weight. Im starting to get frustrated because i feel really gross and ugly and just want my body to go back to its normal size. Im starting to get frustrated because i put so much effort into trying to get it off, i never eat junkfood and i focus on exercise so much. I get enough sleep, and push myself as far as i can every day. How can i lose it faster and what am i doing wrong? My exerciae is mostly cardio so im not gaining weight with muscle and im not starving myself. Youd be suprised how much salad you can eat and stay under 100 calories. Smoothies.

Why cant i lose it? What am i doing wrong?