I'm a male with testicular atrophy. Doctors cannot find the cause. I have little money. How can I store my sperm somehow or will I be childless?

Unfortunately. It is not a medial emergency to seek public assistance or medicaid for such service . Cryogenic storage of your sperm will be expensive , first find out how much it will be, from a sperm bank , then ask your family and friends to assist you. Good Luck .