Depression and Weight Loss

I have been struggling my whole life with weight loss and depression. I used to be able to lose weight fairly easy but then again it wasn't always the healthy way of doing it. I usually lose about 20lbs and then give up on the rest. This last time I had lost about 20-25lbs after my 2nd baby and kept it off about a year till I got pregnant with my 3rd. During the pregnancy I lost my job and decided to just be a stay at home mom. I got extremely lazy being at home all day and started to notice my depression issues again after her birth so I decided I needed to be back on some kind of medication to help control my mood, anger, and being fatigued constantly. According to my doctor I was diagnosed with depression and bi polar tendencies. I was put on Celexa and Risperdal. I have previously been on many different kinds off and on since high school. Since I started taking the new meds I have been more and more tired than I already was and could sleep all day, which some days I almost do. I have become so lazy when it comes to getting things done and its so frustrating! I joined a gym in January and have been working out for about an hour 4 days a week to try to lose all the weight I had gained in the last 2 years and feel better about myself again . I thought that by working out I would see and increase in energy and productivity in myself but sadly I have seen no changes. This last month I have gotten so depressed about it all that I basically gave up on everything and went back to eating junk and drinking lots of dr. pepper. I have since then gained back about 8 of the 13lbs I originally lost since January. I need to get back my motivation to get things going again and not sure what I should do. I don't know if its the meds making me this way or something entirely different. Any help or advice anyone can give me would be greatly appreciated! I can't go on this way any longer, I have 3 children ages 7 and under that I need to tend to!