[maci_mace]

I didn't bother to read all the comments as I know a lot of people jumped to the conclusion that you were abusing the dog because he is terrified of you. I fostered small dogs and bigs dogs, and honestly fear happens for a lot of reasons... this li'l dog obviously has had poor socialization and big lack of training. And seeing as how he is a momma's boy he probably is much more comfortable in the presence of women.
So when you moved into the home right after the other roommate moved out he was probably very frightened to have you there all day.

I have seen a lot of cases like this, including Maci and my last foster a pitbull. The first night my husband came home from work the pitty seriously freaked out, she pinned my husband to the front door with snarling and barking and as soon as he moved she ran into the kitchen and pee'd herself... my husband didn't do a THING to her, she had been raised by a family of 4-5 women and never introduced to men and had been tied to a truck all summer to be a guard dog... so it took a lot of work for her to accept my husband, and she did! And he and her really had a special bond, but is took a long while!

With Maci the same thing happened, she was raised by 3 women, my husband came home and she ran at him barking I picked her up, let her sniff my husband, and put her down... she ran to the corner where her pee pad was and just cowered there. Again, FOR NO REASON at least by no reason/fault of my husband. My husband tried all night to get her to come to him and sleep with him, and she just wouldn't she stayed on her pee pad. So I picked her up, plopped her between the husband and I and her talked to her and petted her and she calmed down a lot even took a treat from him!

If you ignore the blames of abuse there is actually a lot of great advice here! Also, if you go the behaviour and training section MORE great stuff there. You may be using too harsh of a "no" with the dog, and make sure you use little treats as rewards for going potty outside or for not barking. Have you guys considering pee pads? If you have for whatever reason hit the dog, then 1. don't ever do it again and 2. it's going to take a long time for him to forget that.

Since he is used to peeing/pooping in the house you could try peepad training, that could really work wonders! He still gets to pee/poo inside but it has be be in his "spot" on a pee pad.

And last resort, if you and your g/f feel the dog can not stay with you, then find a reputable rescue lots are listed here on YT. Mind you, unless you guys are getting married and know you love eachother and will stay together forever... might be best to just leave. Your gf could end up with resentment if she rehomes her dog because of you.