Eat low carb and exercise 5 days a week, Walk 5 miles a day, weights 3 days and swim 30 minutes 2 days a week for the past few years. Lost 50 lbs but plateaued at around 220 any recommendations.

Congratulations! So much depends on your frame size and metabolism. Please continue under the care of your doc if you are not doing that now. He/she may check your thyroid and other hormones. Maybe you are where you need to be. Peace and good health. Lots of good things can happen on plateaus.
You're doing well! going from 270 to 220 will have a significant lowering of risk of diabetes, hypertension, and heart disease. Of course, you will have about 500 LESS calories burned per day due to the lower weight. Calorie count, estimates of how much net in/out is a first start. Sounds like with an 1800 cal diet, you should be losing. http://www.amazon.com/dp/0692496157/ might be helpful.
Great job!!! See the excellent answers on 'weight loss'. You basically need to burn more calories than you take in. Increase your exercise, choose healthier, less-caloric foods and drinks. The nice thing is that if u build more muscle you will even burn more calories while you sleep! and don't focus too much on weight. Focus more on pants-size, etc. Muscle weighs more than fat but that's ok--its good wt.
Muscle mass. My God, how much more can you do. Cartman on Southpark says it best: "I'm just big boned!".