Yeah I've got my 3 and 1/2-year-old my 2 and 1/2-year-old and my 4-month-old so I understand where you're going. Just try and give him some kind of one-on-one time, whether that's helping you cook a meal. Whether that just reading him a story before a nap or bedtime. Just some kind of one-on-one kind and try and increase it the more you can as you get used to having baby home. Remember you're adjusting to this life but so is he
Sorry you're going through that. It's definitely tough. I have a 2 month old and 3 1/2 year old. What we did was get a big sister book that told her about being a big sister, and she really enjoyed us reading that to her. The book really helped to make her understand what was happening, and what she can do with the baby. We also give her words of encouragement whenever she's home (she goes to day care during the day) about how she is such a great big sister, or when she does something on her own, etc. She still has her moments where she acts out, but we try to remain calm because we know this is a bug change for her. Hope your toddler gets better.