How do I raise my Vitamin D level? Meds just isnt working.

My Dr. and I have been monitoring my vitamin D levels but they stay low constantly. Every time we talk about it, she does test me and comes back low and she gives me a month of prescription for it. I also take 10,000 IU of OTC vitamin D pills every day as well. I do have a bit of health issues like IBS, gastroparesis, chronic stomach pain, chronic back pain, migraines, pre-diabetic, acid reflux disease, neuropathy, anxiety, depression, seasonal allergies, and heart palpitations.
All suggestions and advice will be greatly appreciated. Thanks!