Pcos after 2 babies? and a type 1 diabetic

I was diagnosed with PCOS today from what my lab work came back and have a scheduled Ultrasound in 2 weeks. However; Im not 100% sure what PCOS is? I understand the mists of it from what ive read about it so far. I have 2 Kids (4 and 8 months) my first took me 2 months to get pregnant and my last baby took me 1 year and They did ultrasounds and labwork to make sure everything was good before I got pregnant and they said everything looked good? My period was last month and this month I missed my period completely. Ive never had missed periods or even late periods before until the last two months.. I have Gained/ havent lost my pregnancy weight yet either. I am a type 1 diabetic as well. Could it be a misdiagnosis?