Why Do I Experience Thirst, Weakness In Legs And Heaviness In Head While Walking ?

hi sir,
my complain is when i start to walking i feel likes there is thirsthy in throat,weakness feels in legs specially in calf muscles,also little heaviness in the head in frontal region & feel like imbalance vision,body,i alredy checked up sugar,thyroid,cholesterol,vitamins but my gp diagnosed u have little cyanocobalmin defi so you will need to atleast three months regimen of tablets. and one more important thing is that i have multiple neurofibroma on the both arms,gluteus region,some on back side but its not painful anytime and now i m also have some disturbance in the epigastric region like hardness & feeling of vomitting after taking food,sometimes little feelings of pain in heart,
my weight is 61 kgs,heght is 5 8". i m such a healthy but these all complints since 20 days starting with imbalance when i walk,my routine work out about 3 miles by walking everyday


thank u