What to do?

I am a first time mother and My boyfriend and I have a 1 month old baby and we have had a discussion already about him helping out more with the baby and around the house. He stepped it up for that about a week or two but went back to his old self.  I am on my last few weeks of maternity leave and his two children from another relationship are going to be spending the rest of the summer with us. He will be taking two weeks of leave once I go back to work. I am super apprehensive about leaving the baby with him and his two other children since he doesn't watch her much now. Also, is it selfish of me to enjoy my last two weeks of leave alone with my baby? I am usually excited to see his kiddos but I just can't do everything around the house and watch a newborn and two kids. Am I overthinking things??