Prenatals and weight gain.

Can prenatals help with weight gain? I'm severly underweight. 5'5 and 102 pounds. I've had my wedding ring resized twice, and yet I keep losing weight so it falls off. I just started them today. Of course when I was pregnant, I was gaining weight. But i immediatly lost it all after having my daughter. Dropped 14 pounds in two weeks after having her. And now I'm almost 14 months post partum, still losing. I don't want to go back to 94 pounds. Depo caused me to lose weight drastically. I miss my 120 pounds, hell I would love more weight than that. I'm tired of looking like a skeleton. I eat like a man, yet nothing. I'm tired of being called a crack head, being told to eat a cheeseburger, nothing fitting, it's seriously taking a toll on me. I don't feel pretty at all anymore. I honestly cry about this. Please tell me if this is something that will help. If not, what will?