Toddler adjusting to new baby

R

So I had my first child, my son, on 11/14/16. Nightmare of an infant. But seriously an angel of a toddler. A lot of energy but all in all smart, independent, so loving and sweet.

11/9/19 I gave birth to his brother. His first sibling. This baby is an angel. So calm. Only really cries when he’s hungry. Which is amazing because I’m pretty sure my 3 year old has been replaced by a child I’ve never met before.

It started off with him refusing to bathe every day right before the baby was born. At first I fought It but then I let It go since it’s at least been every other day. Then he started hitting my niece who’s only 1. He’ll literally shove her to the ground. Refuse to apologize and then do it again. He throws tantrums over everything. Like you can barely talk to him without a full on meltdown happening. Recently, he’s even started hitting adults. For example he slapped my mom across the face because she wanted to give him a hug.

I’ve cut out specific time during the day every day for he and I to spend time alone. I’ve given him big brother responsibilities like picking out both of their outfits every morning. I’ve acknowledged good behavior and rewarded him for It. For the bad behavior, I’ve tried time outs. I’ve tried removing him from the situation to cool down. I’ve tried asking him about his feelings and why he’s acted the way he has. I’ve read articles and watched “parenting experts” on YouTube. They often say that 3 is a difficult age and they need to mature mentally. Nothing has worked for us. It’s been about 3/4 weeks of this behavior at this point. I miss my sweet boy. We’d cuddle. Hold hands. He’d tell me I’m his best friend and he loves me. Now I barely get any affection from him in return. I’m so sad. I feel like I’ll never get that boy back.

Someone please tell me they’ve experienced this and that It gets better. Or even have any tips to help him adjust.