Hey, I have two sons (ages 4 years and 10 months) and I had PPD after both births. I am currently taking Wellbutrin, and it is fantastic for both depression & aiding weight loss. Wellbutrin is different from other antidepressants because it is a mild stimulant, so it gives you energy & suppresses your appetite. Other antidepressants like Zoloft make you gain weight. You can't take it if you're breastfeeding though - only after the baby is weaned. I gained 35 pounds with each pregnancy, and it took 7 months to lose it after the first & 9 months to lose it after the second. I am 5'9" and was 150 when I got pregnant with my older son - I am now 154 after the second & trying to get down to around 145 (my ideal weight), a size 6 for me.
You can take zoloft while breastfeeding. (might depend on what country you are in - but in Canada it is ok; LLL)