The levels of saturation of vitamin d3 varies for each individual, it depends on your body mass, your metabolism, and lots of other factors. That means, you can give 2000ui to 50 different individuals, daily, and after a month you can have 50 different results.
Try to first measure your actual blood levels of 25(OH)D3, its a simple lab test. After that you start taking a daily dosage that would fit your body needs, and that can be in a range of 1000ui to 10.000ui/daily. Its really important that you maintain your levels between 50-80ng/dl to help prevent a wide range of diseases. Also, keep in mind that our body can produce up to 10.000ui daily by safe sun exposure.
Consider visiting a doctor or a health practitioner so they can take a better look at your case.
Hope it helps!
Gabriel Henriques