hi im 6` 235lbs 23, i eat every three hours. my diet is good and been working out for the past year and i fine im getting stronger but not bigger

bench 5rep max 290
squat 5rep max 270
deadlift 5rep max 260

when i wake up
protein drink
work out
protein drink
three hours from that i eat chicken(bake or broil)
3 from that is tuna in the can or over a salad
then more chicken the same from the first one
then a protein drink before i go to bed.
i drink about 1 1/2 gallons of water a day

i work out three times a week m,w,f im almost done with the 5x5 im hitting 300 first then im going to do the 10x10