Stress from my oldest

Conie
Pregnant with baby #2 and my 4 1/2 year old has been absolutely terrible. He's always been such a well behaved child until recently. I'm not sure if it's because he knows change is coming or a phase but it's never been so bad. I can't seem to figured out how to manage my stress with him..and I'm only 9w6d. Any advice from mommies of multiples??