If you were allergic to milk or processed food, you would have the allergic reaction
since you first start eating them.
However, to determine any source of malapsorption or allergies, you can ask your gastrohepatologist to perform the specific testing for malapsorption.
Next, I recommend to do the stool examination for ova/parasites, culture for candida and other bacteria to identify why you are having constipation
It is good you started stool softener
, you can also use lactulose
and sena leaves (as tea or pills) later on.
I'd advise to consume large amounts of water (up to 3 or 4 liters /day) and not to force bowel movement until it would come naturally.
When you defecate, please do not hold your breathe, but breathe deeply using your nostrils, and when passing the stool, get your breathe off.
Hope it helped!