Oh friend, I felt this post in my SOUL. Third trimester with my second kid, same exact thing - 2am, both calves cramping like I’d run a marathon in my sleep. Heating pad was basically useless after a few minutes too.
What actually helped me: magnesium glycinate before bed (ask your OB first, mine gave the green light), and stretching my calves against the wall for like 5 min before lying down. Huge difference. Also sleeping with a pillow under my ankles, not just between the knees. Someone in another thread linked achy legs at night causes and remedies - there’s actually solid info there about what’s safe during pregnancy specifically, which I appreciated because half the advice online ignores that.
Your mom’s not wrong that it’s “normal” but normal doesn’t mean you just suffer through it lol. Poor sleep in the third tri is rough enough without this on top. Hang in there, almost there!