Try another network cable, and another network port on your router to rule out any issues with either one of those elements. Also, of course, do a router reboot/reset and consider rebooting your ONT (Unplug it, disconnect battery, wait 30 seconds, and reverse re-connecting the power).
If you're still having problems, you'll want to get Verizon out to figure out why your upload is shoddy. It could easily be due to dirty/damaged fiber.