It gets better. I promise. I promise. I promise. My now 5.75 year old used to run me ragged. The questions. The need for constant interaction and stimulation. The meltdowns because she wanted to do something that she was not physically ready to do.
Hang in there. Remember that the days are long but the years are short. Call in reinforcements as needed. A grandparent. A babysitter. An aunt or uncle. Anyone who has an hour or so to give. Your little ones life will be richer for the time spent and you will have some small breaks!