Perimenopause?

How old does perimenopause start? I have one doc saying I could be in it and one saying I'm too young to be starting menopause (he didn't mention perimenopause). I'm 42 and have had uterine cryoablation and the hubs had a vasectomy. We have 5 kids between us, so we are definitely done! I've been having hot flashes (my private summers) and some nights I wake up with sweaty neck/hair and my shirt will be damp. It doesn't happen every night, though. Sometimes the hot flashes will happen at any time. The rest of the time I'm usually freezing. I am on meds that can cause the hot flashes, but I was experiencing them before going on the meds. I can't tell from my mom's experience of going into menopause because she had a hysterectomy after I was born.

Any thoughts or experiences of your own that might help me figure it out?