Join a gym or get access to more weights - in order to increase your size and explosiveness (sprints etc.) the reps must be less and eating increased. Stick to squats, deadlifts, chin-ups/pull-downs, bench's, shoulder presses/cleans and you'll be ok - do these so that each muscle group is worked well once a week and practice sprinting once a week also. Football activity only takes like 30 seconds per play, then you rest (pretty much) for 2 minutes so training should mimick that activity.