| I am reading your question to say you had some lights that worked off a switch. Then you added some more lights connecting in at the existing lights. Now the all the lights stay on with the switch in the off position until you turn the breaker off.
Definitions. Wire, a length of copper often covered with insulation. Cable, 2 or more wires bound together in an outer jacket, often now NM-B with a black, white, and bare wire in it.
There are 2 ways the original lights and switch could have been wired. A cable could have been run from the breaker to the switch, and then a second one from the switch to the light. Or the power feed cable could have been run to the light first and another cable run from the light to the switch as a switch loop. It saves material and time to run the power to which ever is closer.
If you tied into the connection between the power feed at the light and the hot wire to the switch, that wire is always going to be hot, and the lights are always going to be on. Pull the cover off the switch. If the box only has one cable in it, then it comes the light and is the switch loop. Another give away is if the white wire is marked black, and was connected to a black wire at the light. You will want to reconnect the black and white wire that went to the switch the way they were, and then connect the new light to the black and white wires at the old light. | 
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