M.D.
So sorry! I am a person who needs some time to myself sometimes, too! Can you arrange a day off (or a few hours) on a weekend? I also recommend that you find a support group for special needs - they may have resources to help with caregiving. This situation is tough on all relationships - mother daughter (your mom and your kids with you), SOs, co workers. It sounds like the relationship is over with SO, but with your mom, hopefully it will change soon.
I don't have much advice, but you definitely will be a better mom, daughter, SO, if your needs are met. Easier said than done, and good luck!