Weight gain: bloated

I had my second child almost 11 months ago, and ever since I had her I keep gaining weight, a few pounds slowly. My weight was supposed to go down, not up! I'm so used to being skinny. My nickname used to be skinny Minnie even after my first child. But not anymore and I'm not used to being this big. I hate it! It's hard to find clothes to fit me. It makes me depressed. Some days I feel so bloated it's disgusting how it makes me feel. I try to eat normal no big portions & not too much sweets. Exercise at least 30-45 minutes walking everyday but nothing..... But I have been drinking wine quite often now and I wonder if that could be it. Has my body's metabolism changed now,Does anyone know what it could be??