I change some water lines the main cold is 3/4 hot 1/2 and why I can't get pressure

I wish you had contacted us before you started to repipe. What has happened is that in moving the pipes some mineral build up in the pipe wells has broke loose and is now clogging. What you failed to do was to turn the water back on foe a few seconds and flush the trash out. WE can help but first we have to know exactly what's not working. What faucets? Hot , cold or both? I need details, Back tom you, Tom