Getting 3 year old to sleep

Anyone struggle with getting their toddler to sleep on their own? I know it’s my fault. We co slept til he was over a year and a half. And he has his own room now, but I lay with him every night to go to sleep. I’m 15 weeks pregnant and it’s getting harder for me to lay with him and get in and out of his twin bed. Tonight, we’re trying to have daddy put him to bed by himself and he’s having a complete and total meltdown. My heart feels broken and I just want to give in and go lay with him but I know I have to cut the ties a little bit. Especially with a new baby coming. Any advice??