Confused

I haven’t had a period in two months. But in the last two months I’ve gained weight, gotten a new job, and started vet school. My job and school are primarily filled with women, and I know this can change my cycle. But could it throw it out of balance for two months? I know I’m not pregnant because I haven’t had sex in forever, but I’m worried about any PCOS or otherwise notable diseases. Does anyone have any input?