Hey, congratulations on your new arrival.
It’s hard with 2 I know and one thing I can say is it does get easier but it’s quite exhausting in the mean time. Your 3 year olds world has just completely been blown apart, everything he knew has changed and the people he had full attention from are now busy and trying to divide themselves in half.
I found that my eldest used to come in to see if he could sleep with us as the baby was in our room he felt left out, for a while we used to go get in his bed for a couple of hours (he had a double bed) just so he could cuddle up and we all got some sleep.
The only thing I really made sure of was that we had lots of quality time when I took him out and left the baby at home with Dad so it made him feel special, I also got him to help me lots with his little brother so he felt included.
For a rest you could put a nice film on he likes and get him to cuddle up with you and the baby when you have them both?
Not much to add just to say it goes so fast with 2 I’m sure he will settle soon x