Your doctor is trying to reach 80nmol/l (32ng/ml). As stated before we believe in maintaining a “healthy” level of 50ng/ml (125nmol/l). Research already shows that at levels below 40ng/ml, your risk for cancer and autoimmune disease rises dramatically.
Your doctor is WRONG! He is cutting back on the amount you take when you haven’t even reached the bottom end of the range. (If anything he should have given you more.) It takes about 8 weeks of taking the same amount of Vitamin D to know what your level will end up to be. So you have taken it long enough and you are not overweight. That means you are not taking enough OR your IBS is keeping you from absorbing it OR in a disease state you are using it up really fast.
So since it could very well be an absorption issue, here is my recommendation. You could first ask the doctor why he would “decrease” the amount you take if you have not reached the goal to begin with and see if he will put you back on the 60,000iu a week. (This would keep some money in your pocket.) If he will not or you just want to do this on your own, do the following.
Get enough Vitamin D in capsule form to take a total of 60,000iu a week. In your instance I would recommend Biotech brand so we do not have to worry about it not having the stated amount of Vitamin D in it. That will at least not allow you to backslide and “can maintain what you have gained”. Then get some oral spray. Here is an example at https://www.amazon.co.uk/s/?ie=UTF8&keywords=vit+d+oral+spray&tag=googhydr-21&index=aps&hvadid=48452352498&hvpos=1t1&hvnetw=g&hvrand=8983363276561059315&hvpone=&hvptwo=&hvqmt=b&hvdev=c&hvdvcmdl=&hvlocint=2826&hvlocphy=9008239&hvtargid=kwd-19726906343&ref=pd_sl_4u5sbtx0zk_b. I cannot vouch for this brand but I do know that oral sprays do work. If one spray equals 3000iu, then I would use “two” sprays or total 6000iu. http://www.greenvits.eu/collections/vitamin-d also is a supplier of Vitamin D but no sprays.
At 11 weeks you are due for a recheck. If your levels increase a lot, then you will know that you need to take the oral spray at least for now rather than capsules. If the levels barely increase again, then it is plan B to be discussed then.
Hope this all makes sense. If not let me know!