The trouble with chewing tums to get calcium is that it is an antacid and reduces the stomach acid needed for digestion. If you use them don't use before or after meals.
Another thing that reduces calcium in your bones is sodas. Sodas contain phosphoric acid and calcium is leeched out out your bones to neutralize it. So lay off the sodas.
milk is an excellent way to get calcium - one of the best ways. Skim milk is the best choice for lower fat content. It also has protein in it, which does not have a detrimental impact on the calcium. In addition, take calcium supplements with vitamin D (with meals for better absorption)