My 2nd newborn is 7 months old. Is it contributing.?

This. 3 and 1.5 here. If you are pulling your weight (or more) at the homefront then there is no time/energy for much else beyond staying afloat.

For sure! In my experience, rock bottom parental tiredness is at 3-4 months old due to cumulative sleep deficit at that point and baby doesn't sleep through yet. So only a few months on from that, I think you're beating yourself up about work. Its fine to feel less motivated about work as a Dad of young kids. Speaking as a Dad of older kids now, over time you develop efficiencies at home and at work, and in the end you can become good at both doing plenty enough to please your employer, whilst keeping hours of work sensible to enable family time too. So then motivation and focus is no problem. Providing for a family can be a good motivator. (caveat - this requires working for a decent reasonable employer and having a job role that matches your skills well. this can sometimes involve a job move or two to get to)