Talk to Dietitian/Nutritionist on Severe Knee Pain VitD 6.4

Hi, I posted a dew days back regarding recent searing pain in my knees and general body fatigue. Cavities developing in teeth and whitening of hair in the last few months. I then took a few blood tests and Vitamin D and Calcium tests. All test results are in the recommended range except Vitamin D3, which shows 6.4. A bit of internet browsing gave me an idea that is is extremely low. I am now quite worried, and need to see a relevant doctor immediately. Someone please recommend. I am afraid the doctor will prescribe me very high level of IUs. Apart from supplements, I am planning to go out on morning sunlight for natural build up of Vitamin D. What food items do you suggest me to eat for natural intake ? Thanks!