I have had off and on excessive belching for 6 months now. It all started after antibiotic treatment. My MD doesn't seem concerned. How do I stop it?

Burping issues. Involuntary belching after a meal is normal, caused by release of swallowed gas after distension of the stomach with food. Magenblase syndrome is postprandial epigastric fullness & bloating, relieved by belching. Aerophagia (accumulation of gas due to air swallowing) is common with anxiety, hypersalivation from gum chewing, smoking, drinking, oral irritation. In some, belching can become habitual.
Probiotics. GI upset is not uncommon with antibiotics - while persistent symptom for six month is somewhat unusual but not impossible based on our understanding of normal GI flora and changes due to antibiotics and infection. You could consider taking probiotics products like kefir - which is inexpensive and readily available. You can also consider more expensive products like Bio-K. Twice a day with meals.