17 month old cannot fall asleep on his own

[ilovemyboys3]

Just seeking some advice - if anyone has any wonderful tactics.
My 17 month old is a great sleeper, sleeps 12 hours every night and has done since 5 weeks old!
The issue is... he still cannot self soothe or settle on his own. He falls asleep with a bottle of milk or me holding his hold or just generally sitting with him. If I attempt to leave the room whilst he is still awake then he stands up immediately and cries.
This hasn't been an issue so I've carried on to comfort him whilst he falls asleep. However, I'm currently 40 weeks pregnant and worrying how I'll sit with him until he falls asleep. Sometimes takes 45 minutes. What will I do with the baby. My partner works shifts which are mainly afternoon/evening so is rarely there at bedtime.
I'm starting to worry how I'll manage.
My older child self soothed from 10 months and was just a case of saying night night and he would lay and fall asleep.
Should I try controlled crying? Is he too young? Or have I left it too late? Any advice? Many thanks