Alternatively, have you maybe been giving him more freedom around the house, since you thought he was doing so well? And thereby giving him more opportunities to have accidents? If so, I would dial back the freedom a lot. Keep him close enough to grab, or else crated, at all times, and take him out on a very frequent schedule. A dog who was having 2 accidents a day is not housetrained, btw - and a 14 week old puppy is just a tiny baby who has no control over pottying. He probably doesn't understand that he's not supposed to pee inside, and couldn't stop himself if he did.