First, why do you think that your chol and tris are "too low"? They are lower than most people--more than likely that's GOOD. My total cholesterol is 123 and someone here is 107. This is considered "heart attack proof" or near it. But many doctors have never seen TC that low so they may think it is somehow dangerous. My own doc said she'd never seen a 123 before me.
If you are underweight, increase fat a bit, sticking with nuts, avocado, olives, etc. (not extracts like oils). Add tofu to your menu. Get to a low-normal BMI and recheck TC and tris after a few months of being at a normal BMI. Whatever you get at that point is probably very healthy.