I just don’t know what else to do

I’m so defeated. My miniature American shepherd, almost 5 months just will not house train. I take him out constantly. I couldn’t possibly take him out more. He goes AT LEAST every 30 minutes AND will go out on his lead a couple times a day. We don’t have a fenced in yard or doggie door. He pees every single time. Even if just a little he definitely goes each and every time. He knows to potty outside but he hasn’t figured out to NOT also go in the house. We’ve had ZERO days accident free days. We were so close today, and lo and behold I see a puddle in the floor. I have no idea when this could’ve even happened. He’s in his kennel when he can’t be observed. What’s also perplexing is that he sleeps 9 hours in a kennel overnight and holds it allllll night. Please help. I’m so over this. It’s not even been long but it feels like a lifetime.