I don't work and I only have 1. But what's your saying sounds like a normal emotion. When you are away from your kids it's normal to miss them. Your not useless. Maybe if you are up for it and your job allows this, take a vacation or some sick days and spend time with the kids. But your not useless and even if you don't see it now you will. The love you get from your kids shows that the know you love them and your important.
Wouldn’t it be better for you to be with your kids and your husband to work?
There was a period of time when I worked, and my now ex-husband watched the kids. He sucked at it. I never felt useless, but I was sad because I was missing out and angry because I knew I could do a better job than him. As long as they're taken care of properly, don't feel useless. Be proud that you are a great provider and that you chose a capable partner.
Your doing your best for your kids it sounds like you have mom Guilt which Is normal I feel the same about starting work maybe try to make it up to them in other ways spending dedicated time with them on the days you don’t work or search for a job closer to home