New dog (But he needs time and patience)

So I just got a new dog yesterday, he’s a 3yo chihuahua mix and he’s somewhat potty trained, (he doesn’t go on the floor, but he goes on pee pad) and I’m unable to get him outside, I don’t want him to get used to going in the house, but I also don’t want to rush him and make him overwhelmed and uncomfortable with me. However he’s only gone pee twice, once when I first brought him home (outside) and then this morning around 5 am? (Inside on pee pad), but then he goes right back in his crate and sits and sleeps all day, he’ll eat but won’t drink water yet. Idk what I can do? He’s very skittish and shy, he won’t even let me put his harness back on that the shelter gave us, he had it on but he slid out of it, and they said not to take him outside without a harness or a leash. So I’m struggling, but at the same time, I want to be patient with him. Please help.