Puppy refuses to use the bathroom outside

Hello, I’m looking for some advice on my new puppy (who is a four month old corgi x terrier mix if that’s helpful). I adopted him a few days ago and love him so much. He and I bonded very quickly and so far he’s adjusting to his new environment great. The only problem is that potty training seems to be a big issue area for him. I’m not sure if his previous owner had him using puppy pads or something of the like, but I’ve strictly followed all of the standard potty training advice to no avail. I keep him under my supervision at all times and always catch him mid-accident. When I relocate him outside, he refuses to go no matter how long we stand out in the same little patch of grass (5 minutes, 10 minutes, 30 minutes…) and will hold it until we get back inside. When I interrupt him mid-accident again, the process simply repeats. In fact, I’ve stopped him so many times I’m beginning to fear that he thinks that going outside is a punishment for going to the bathroom…he’s started to try and be sneaky when he has an accident despite me never yelling at him, never making loud noises at him, and never even telling him “no”. I have tried to use only positive reinforcement throughout the duration of all of his training. It has worked in every other instance, except for this one.

I also follow a strict routine by letting him out as soon as he wakes up, shortly before we go to bed, 10 minutes after eating his meals, and about every hour to two hours throughout the day (I’m a university student so I do have to leave for class at times, however I live within walking distance from my campus, take the bus to get to him even quicker, purposely structured my schedule and even dropped a class so that I’m not leaving him for more than two hours at a time). I’ve managed to get him to pee outside a whopping single time and practically threw a party to praise and re-enforce the behavior. Afterwards, he immediately peed even MORE inside…in his sleeping area in fact, which is definitely new and has left me quite discouraged.

My aunt did send me a package of puppy pads (she trained her own dogs with them), although I have yet to use them because I would definitely prefer for him to use the bathroom outside. However, with the exception of a single corner of my room, I’ve noticed he prefers to pee on soft surfaces (e.g. my rug and now his bedding). Would it be a good idea to try using the puppy pads at least initially so that he doesn’t start to think the rug and his bed are fair game, and so that he doesn’t think I’m upset at him for using the bathroom at all, or that going outside is a punishment? After that, is there a good way to transition from using the puppy pads to peeing outside, or will the texture association be too strong to break? I’m especially worried about what that would cause if he and I were to move to a living arrangement with carpet in the future. My current apartment has all hardwood floors but I definitely don’t plan on staying here forever.

One more thing to note is that it is a short walk to get outside from where we live. We are on the first floor but we have to walk down the hallway and turn the corner…maybe this is contributing to his reluctance/confusion especially when I relocate him mid-accident?

Any advice and suggestions are appreciated. I grew up with dogs in the past and none of them have been this difficult to train. I’m worried I’m doing something wrong that I’m simply not aware of. He is such a perfect little guy and I just want to give him the best home possible.

Thank you!