Sometimes lactose intolerance is a side effect of other problems. Basically your intestines produce lactese which is an enzyme that breaks down the sugar lactose. When there isn’t enough, you can’t tolerate the lactose. We naturally produce less as we age of course, but if you had some other problems (in my case a soy intolerance I was unaware of) that is irritating the intestines, it will produce less lactese (among other problems). Once I was able to identify my problem and started eating right, my intestine began to heal and I was able to tolerate more dairy. Not saying this is your problem, but definitely something to consider. Best to consult with a doctor to see what’s really going on.
An old dairy farmer told me this: pasteurizing milk destroys the lactase enzyme that is present in the milk. Drinking unpasteurized milk helps with mild lactose intolerance. No idea if it’s based in scientific reality.