I'd suggest adding an extra day or two of training per week. If you've been doing full body, split it up along the lines of:
1 - Squat, bench, couple of accessories
2 - Bench, heavy rows, couple of accessories
3 - deadlift, press, couple of accessories
4 - Squat, press, couple of accessories
If you can add around 10 lbs a month to your lower body and 5 lbs a month to your upper body on your heaviest work sets your progress should be on the money. Remember that those increments are on your heaviest work sets, and will likely mean a much larger increase in max lift. After a while, you'll find yourself using your max for your heavy work sets. When that happens, you will know for sure that your max has gone up a lot.
Max squat 220 lbs
Heaviest work set 5x176 lbs
Add 10 lbs per month for three months
Heaviest work set after three months 5x216 lbs
Heaviest work set after another month 5x226 lbs - your max now will be MUCH higher than 220 lbs, after only 16 weeks.
Also clean up your diet and consider eating more but higher quality food.