For a few months my toe nails have been breaking off all most completey off with no pain at times I don't even notice it breaks off. What is causing it?

Few things. Can cause this. Fungus or trauma (even micro trauma) are some common reasons as are vitamin deficiencies. (microtrauma can occur by ill fitting shoes.) see a podiatrist who can help make the diagnosis and offer a treatment plan.
Malnutrition. I would suggest that you talk with your doctor asap -- you may have some kind of malnutrition perhaps involuntary due to some malabsorption problem. The symptoms you describe is usually caused by mineral and electrolyte imbalance --.