Luger9

If by your description, you have 3 TVs and a cable modem, then you need 4 signals. To get the best connection to your internet, get a 2-way splitter and a 3-way splitter. Put the 2-way on the line coming into the house, send one of the lines directly to your Cablemodem, the other line goes to the 3-way splitter. Now run the lines from the 3-way to your TVs. This would be the most prudent way to check to see if the problem is in your wiring.