Well, hopefully you have arrived at the right place to sort out the problems. First a few questions:
1. Does this problem occur for wired or wireless connections or both?
2. Can you copy and paste the DOCSIS WAN downstream and upstream tables from your modem and paste them into this thread. Those are the cable signal levels and signal to noise ratios. The first item of business is to determine if the modem itself is operating properly with the current signal levels. The instructions for logging in and finding the tables are shown here: