37y-f. Being treated for acid reflux infection & myoplasma infection since 2wk. Sudden painful swelling on left side of chest, under armpit since yest?

This may be. completely unrelated to your other issues but is certainly something that should be brought to the attention of your health care provider. It sounds like the development of lymph node swelling or an infection. Either way it should be seen and evaluated. Make an appointment for today.