What was your vitamin D level when you stopped mega dosing? the vitamin D council has stated that your level must be in the 70 range before your body starts storing reserves. And if you are overweight, your needs for supplementing are even higher.
In fact, it seems like the more is discovered about vitamin d by competent researchers, the higher the minimum level goes. It used to be that 30 was good, then it got bumped up to 50, now they are saying 65 is good. And if you have any chronic conditions, your level should be above 90.
Personally, I want my levels to stay in the 80-90ng/ml range