Could this be lactose intolerance? i have never had that before but can it onset late or suddenly?

Yes ..but: As many as 1/4 of the adult population will have lactose intolerance after childhood. It can also develop transiently after gut injury during a bad diarrhea illness (lasting up to several weeks). In many cases it just reflects a bad balance of gut germs that create more gas & these can be changed/improved with probiotics. A diet change to foods that trigger more gas can also be the issue.

"This" means what?..: The great majority of the world's population becomes lactose intolerant with age (except northern Europeans), because people produce less and less lactase enzyme and will not be able to digest milk sugar. Lactose intolerance can come on more suddenly after a diarrheal illness. Taking lactase tablets can help a lot. We humans are the only mammals who keep drinking milk after weaning off the breast.