This is what I've done in terms of troubleshooting it myself:
-Removed all unnecessary splitters.
-Wired PC directly to the modem (tried 2 different PCs, 2 different ethernet cables) to check internet connection after it went down.
-Hard reset Modem and Router.
Right now the only way to regain internet connection is by rebooting both Modem and Router.
My next plan would be connecting just a computer to the modem and leaving it connected for 1-2 days just to further isolate the problem.
What I don't understand is why are both router and modem not giving me any LED light indications when the internet goes down? Why does the connection status in modem and router web page says its "Good". If either modem or router is bad then why my connection is all good after reboot?