You're not alone, I think all toddlers go through this stage, and throw into the mix a new baby, and its hard for them to adjust.

Have you got a sling for your newborn? I found if I put DS in that, I could then sit and do craft or playdo or something with DD. When we got to cranky o'clock, DS would go back in the sling, and DD and I would sing or we would walk up and down our long hallway, doing big steps, little steps, and so on. DS was happy because he was being held and we were on the mood, and DD was happy because I was doing stuff with her. Stickers were always good at distracting her when I was feeding DS, and tbh, the tv was a bit of a lifesaver in early days, as it was winter.

Have you got someone that can take DD for a break, and then maybe leave DS with DH or someone, and just take DD out for a special treat, without your DS? I also had DD in childcare 1 day a week, and I think we both needed that.

It is a stage that we all go through, so be easy on yourself