The problem may be low pressure or it may be low flow.
Tell me when you first turn on the water is the pressure good for a second or two then drops off?
Many people go to the RV store and get an RV water pressure regulator, this is a brass or plastic cylinder about 3/4" in diamater with male and female hose fittings one on one end the other on the other.. Some have a bright plastic grip on the female end or wings on the plastic body, THESE ARE JUNK and should be left in the store.
Valterra makes an adjustable. Friends who have tried it say it's OK
I have both a Watts and a Zurin and a Sur-Flo The Sur Flo is the one built into many RV's.. WHEN NEW these all worked well, I give the Sur-Flo a 9 and the others 10+. As they age they do "Slow down" and become more like the cheap cylinder ones above, but they can be easily rebuilt.. Though I've yet to get the kits.. More a "yet to get" than anything else.. I mean it took me six months to get a new ladder to replace my little 2 step job. And that is a needed item.. So imagine how long it will take to get the rebuild kit :).