Kee losing internet

Hello, i just set up a new internet connection at my house with modem and wireless router i am using a splitter
(tv and modem) it was working but i keep losing the internet and getting it back and on the modem the cable light is flashing is it a bad cable? or is it the splitter, or the entire plugin!!? its not the wireless router because
i plugged the modem into my laptop and still kept losing the connection the signal is excellent when wireless
so i dont know could the tv be intrfearing with the connection? i dont know i have tryed everything i am out if ideas pleasse help!!!!!!!!!!!!!!!!!!!