hey, i play football too! what position r u??
look, keep working out at the gym thats good...but in the food topic, u should eat a lot of fruit, vegetables and proteins, like nuts, meat, fish, beans, bread, milk!! etc!!! the proteins are for your muscles to keep them healthy! and the fruits and vegetables r for the rest of your budy, they will give u energy and a lot of stamina! thats really important in football and u know it! try to eat things like bananas, apples, tomatoes, potatoes, onions, salad etc...
good luck, take care and remember, no pain no gain! hit hard!