Personally, I wouldn’t say so, but there are two possible problems: first, check the carb count, just to make sure you aren’t getting too much; and second, you might possibly have a sensitivity to one of the milk proteins (more common with cheeses made from cow’s milk, rather than milk from sheep or goats). But aged cheeses usually don’t have enough sugar to worry about (whether on keto or as a carnivore), because the bacteria used in the cheese-making process will have consumed most, if not all, of it. And not everyone is sensitive to dairy proteins. You have to go by what works for you.
It depends on what you mean by constipation. If you mean having pain and having to strain while moving your bowel, then no carnivore doesn’t cause that (though not getting enough salt can cause it). But if you mean infrequency of bowel movements, that is usually a perfectly natural and normal consequence of a carnivore diet. Unlike fibrous plant foods, meat is highly digestible, and there is less waste, hence we don’t need to move our bowel as frequently. This is usually true on a keto diet, too, unless people go out of their way to consume fibre.
But magnesium and dietary fat are good ways to “grease the skids,” so to speak. And if you increase your salt, you may find that too much salt also has something of a laxative effect, whereas too little causes constipation.
P.S.—Let me join Robin in welcoming you to the Ketogenic Forums!