Haven’t gotten my period since august

So I had a procedure in late august following a surgery complication. But since then I haven’t had my period and I been taking my birth control pill daily. I am not sure if it is the stress after and with school, the brand of the pill, or if my body is going through changes. I noticed a generic brand in the past caused me to get sick and not have my period so I stuck with one but I changed doctors and that’s all my new insurance is going to pay is a brand called Portia instead of emoQuette. Can someone help me out?