Why does my leg keep falling asleep?

Ok so I am 21 and yes I'm a bit chubby im 200 pounds even and have bounced between 200-205 pounds the last few years of my life. But I have never had this problem before. My right leg continuously falls asleep and my foot when I lay down or sit down the only time it doesn't fall asleep or feel like it has no circulation is when I am standing or laying flat on my stomach or back. If I sit or lay on my right side my entire right leg and foot will start to go numb within minutes and this process has been happening going on 2 months now. What could this be ? I am over weight but not serverly and I drink water everyday so I am confused as to what could be going on. Anyone please give a little information !