Leg and hand pain after mild workout.

Hi Since childhood I have noticed I get leg pain even walking short distance or similar distance as my friends when I told this to any doctor they all told I was just weak and to rest and  to avoid that pain I never involved myself in any physical activity As I grew older i realised there is something wrong now I am 29 years old I wanna find out why. I get leg pain just climbing till first floor Last year i took a blood test as the doctor suggested i found out my vitamin d3 is severely low and my cpk was more than  2000 I had to move from that place and didn't connect with the doctor for work reason Tbh I am scared they might tell it's something bad I wanna know what I should do? I take 60,000 iu weekly vitamin d3 solution Somedays i don't have pain when I do the same activity on a lucky day but usually it's not the case. I started working out and I get tired easily I get all the news that cpk high with workout might get worse but I don't have kidney pain or anything such