unhook your hose and see (roughly) how long it takes water coming out of the tap to fill a container .... then reattach the hose to the tap and disconnect it from the camper .... turn on the water and see if it takes roughly the same time to fill the container .... if it does, the problem is most likely in the camper with the backflow valve and/or screen washer at the camper's water connection being the prime suspect .... if it takes markedly longer, the pressure regulator, filter, and or a hidden kink in the hose are the prime suspects .... as has been noted, to get by until the problem is taken care of, using the camper's fresh water tank and pump is a good alternative
Jim