Why would a doctor fire a patient? Dont they know we are sick and stressed?

You have the right . To seek the advice of whomever you want is your absolute right. To not see you, ours.
Ask your doc. If you don't know why that happened. Common reasons include poor compliance with recommended treatment, deception, routinely missing appointments, abusive behavior and drug seeking behavior.
Bad fit . Feeling poorly or stressed doesn't give anyone the right to be rude or abusive to their physician. On the other hand the physician might be a complete ass. Who knows? If you completely ignore the md's advice then the relationship should be severed. If you don't feel the advice is sound, go elsewhere.