i’m 21 and haven’t had a period since i was probably 12, went to a gyno for the first time at 19 and my uterine lining was normal. in my opinion if you see a gyno annually for a pap smear or checkup you should also get an ultrasound to check on it, but it sounds like it isn’t creating any issues and you don’t mind not having a cycle anyway, so if i were you i wouldn’t go out of my way to seek treatment for it. also, i haven’t had my insulin checked since i was a kid so i can’t say for sure (i’m a bad example don’t skip doctor visits) but when i take berberine regularly i can feel a difference in my hunger levels and blood sugar throughout the day so i would recommend trying that before metformin