Water boiler pressure?

Ok i recently baought a new water boiler because my other ones seal like on the tank broke and leaked... so. I baought another one like 10 -5 gallons smaller its electric not gas yea so now i. Hooked everything up amd put it how it was and i cleaned the water softner hooked that up ...i have a 2 story house no basement so when i wash clother and take a shower barely water comes out and out of the facets or when i flush the toilet then wash my hands i have to wait till water is filled in toilet or two people shower and one shower barely water comes out....how can i put more pressure? Or what do u think is wrong