I had asked for some additional information and have not heard back.
There are several considerations that could be causing these symptoms.
Acid reflux, also called gastroesophageal reflux disease, or GERD, is a common cause of chest pain and also can cause irritation of the lungs, causing symptoms similar to asthma. Since you were advised to take antacids, this was apparently suspected. If antacids are not sufficient to control acid reflux, then it would be appropriate to consider a medicine that suppresses the release of stomach acid, such as ranitdine or omeprazole.
Another common cause of chest pain in young adults is from musculoskeletal inflammation of the rib cage, and is, in fact, the most common cause of chest pain in young adults. Musculoskeletal inflammation does not directly affect the lungs, but the pain from movement of the rib cage can be perceived as an effect on breathing. If there is tenderness if you press in the area of pain, that is more suggestive that it is due to musculoskeletal inflammation. In this situation, an over the counter anti-inflammatory medicine, such as ibuprofen or naproxen, would typically be helpful.
If I can provide any additional information, please let me know.