Hello ma'am and welcome.
Surgery is stress
for the body physically, it can result in temporary irregularities in the menstrual cycle but not permanent. The more likely cause as I see it is either age or the pill that you have taken. The pill has a side effect of causing irregularity in the menstrual cycle for quite some time.
Please speak to your doctor about the same, as this irregularity has resulted in a hormonal
imbalance which is also causing acne
Hope this helps.