Hi aerowelder,
One thing to try is running off the pump to see if you have good water flow from the fresh water tank. If so, it would indicate the problem is either at the connection to the trailer or earlier. You should also disconnect the water hose from the city water inlet and check to see if there's good water flow coming out of the hose. Take a look at the city inlet filter screen; it could be partially clogged.
If you're using a pressure regulator, and it's important to do so, it may be restricting water flow as well as pressure. You can read more on the subject at the
RV Water Filter Store.
If you're using a water filter, it could be clogged with debris that's restricting flow.
Finally, in the Heartland User Guide (HUG) section of the forum, we have an owner-written
Water Systems Guide that may provide you with additional insights.