High needs baby

My son was so predictable and easy when he was a newborn. Up until 3 months old. He never really slept through the night ever. Which is fine. But at least I could pretty much keep him satisfied all day. Now my son is 9 months and has bad separation anxiety. If I leave him in his walker and go down the hall he freaks out. If I walk away from his sight at all he gets so upset. He wants me to hold him a lot, just to walk around the house. He loves to see everything. He has a fear of missing out. He wakes up literally every hour or 2 at night. I am so drained. I never get time to myself. I know it’s temporary. But is there anyway that he could have just randomly become a high needs baby just all of a sudden? Because I remember with him being a newborn it didn’t kick my ass as much as now.