SVT

It could be stress, it could be anxiety, it could be lack of sleep/poor quality sleep, comorbidities in kidneys, liver, lungs, vascular disease, GERD, visceral fat, diabetes, virus, chronic inflammation, poor diet, insufficient magnesium or maybe potassium in the diet, other medications that your system is slowing developing an intolerance to, allergies, sleep apnea hitherto undiagnosed and untreated....the list is lengthy. Cold medications, caffeine, sugar...they too are problematic for some sufferers of SVT and AF.
Generally, arrhythmias are progressive in nature. The heart, once it is disordered electrically and develops ectopy or other arrhythmias, is likely to commence a process of remodeling. This changes the substrate of the myocardium that will include deposition of collagen and the development of fibrosis. There might be vessel enlargement involved, and if that goes on for some time, mitral valve prolapse and eventual heart failure.
Medications work for a while for most people, sometimes a good long while. They tend to lose ground over time and the arrythmia takes over again, gaining the upper hand, or a new arrhythmia/series of them takes over. In many cases, after consultation with an electrophysiologist, a catheter ablation procedure can stop the arrhythmia. I urge you to see a competent and highly regarded electrophysiologist (EP) right away.