How old are you?
Have you had this before?
When did it start?
Is this like a crushing feeling? Does it go into the shoulder or upper arm? Are you having other symptoms, such as nausea?
How long has this been going on?
Did the tums help any?
The burning sensation in the middle of the chest is probably likely due to acid reflux disease, or "heartburn", causing by excess stomach acid "splashing" up into the esophagus, causing the burning sensation in the chest.
However, tums usually helps with this.
As it is impossible to evaluate this over the Internet, if you are having this burning chest pain which is not relieved with antacid medications (you could also try Maalox, or Pepto), it may be best to have this checked out in person, because another cause for chest discomfort could be due to the heart, and though unlikely, one would not want to miss the potential serious condition of a heart attack.