You do need to decide if hes allowed to potty in the house, or if he must only potty outside - both gives mixed messages and the result is a dog who wants to potty on soft furnishings (v similar to the potty pad feel!).
Dogs are FAR more discriminating about surfaces and texture than they are about WHERE they potty, so IF you want your dog to go indoors, teach him to go on a substrate that is sONLY found in the potty place.
Effectively that means using a tray filled with turf or gravel/dirt similar to the surfaces available outdoors as you can be sure these are NOT recreated around the house. As I say, potty pads feel to a dog much the same as carpet, bedding, sofas etc!
There is probably something else going on here too - in fact a couple of things.
Firstly, HAS he learned that toiletting in front of you earns him a reward (ie, you take him outside, he goes, you reward him) - has he learned ever that going in front of you gets him shouted at??
Secondly, being away from home, particularly as a juvenile dog still developing his personality and body, is a stressful experience and pottying in places that smell like people *(beds and sofas are top for this!) is a very comforting thing to do that aligns his scent with yours and makes him feel secure.
I would not allow him out of your sight.
Swap the potty pads for a tray with turf in it.
TAKE him outside frequently on a leash and reward him for pottying.
If he makes a mistake DO NOT YELL or tell him off in anyway - at this stage it will just undo your teaching him to potty in front of you outdoors.
If you go out and he doesnt go, come back in, go out again almost immediately. You will have to go out a LOT until you figure out his schedule an dhe figures out its rewarding to do it with you there.