First born so clingy

I am having a really hard time. My son (3 years old) is really struggling. He has gotten to baby level clingy and I honestly don’t know what to do. He’s refusing to sleep unless I stay in his room until he falls asleep. Always wants to lay on me, sit next to me or keep me in his sight. He is starting to wine and cry a lot. All of this is totally outside of his character. He’s always been a mama’s boy but is usually pretty independent. I feel like I’m already getting touched out and the baby is not here. Please tell me if you’ve been through this and any advice.