I have hashimoto thyroidism, pituitary tumor, seizures, lesion on my brain and had multiple concussions. My calves are hurting bad what could this be?

Wow- a lot! This can either be as simple as muscular if you have had any changes in excercise or even trauma (fall, seizure). Or it can be neurological, neuropathic pain due to your comorbidities or even the brain lesion. Or vascular such as a DVT or blood clot in your veins. I would recommend that you get evaluated at your earliest convenience.