Are you getting enough water in your system?
If your not drinking a lot of water then your body is in need of it. Water is the one thing that the body needs more than anything else. Water breaks everything else down and is the one thing that cannot itself be broken down (in the body). Water dehydrates your body and helps everything work better. The more water you drink the better you will feel. If you have trouble drinking water their are ways to motivate yourself to drink more. Start exercising which is good for you anyway, then carry a waist purse water bottle with you. When you get thirsty trust me you will want to drink that water!
