Been having a pressure type feeling in the substernal area. ever since playing softball on friday. played lots before but never had this after playing. i experienced it for a few weeks it went away then came back after friday. worried it's my heart?

Hard to say for sure: New chest pain or pressure needs to be checked. If you have constant pain for weeks it is not likely due to typical heart disease, but still needs to be checked, especially since it came back. You are exercising, thank goodness, which is important to prevent heart disease, now and in your future. Chest pain can be due to heart, lungs, gut (GI symptoms like reflux), bone or muscle disorders, etc,