weight loss shakes?

I'm 5 months pp and I gained 70 pounds in my pregnancy. :( I weighed 121 pounds before pregnancy and I'm trying to lose weight. In the first month pp I weighed 165 pounds and now I weigh 170? I've been walking about a mile on an incline everyday (except weekends) and working out my legs and arms. I drink almost a gallon of water a day. I don't know why I gained weight when I'm working so hard, maybe it's muscle that I gained? I work out my legs and butt every other day and I mean I work them out hard! I feel and see a difference. I also wear a waist trainer and that seems to be working and I've been losing inches and some belly fat, but I'm still not satisfied. I played soccer and I've been active my whole life so I'm not use to being this big. Right now I feel like I'm stuck. I want to try a meal replacement shake that'll help me lose some weight. I tried Herbalife before and it worked but it's too expensive and it tastes like crap. Can anyone recommend something? Perhaps you all have tried something that worked for you and I would like you to share please. :)