Housebreaking my puppy; he's got it half down!?

I have a little puppy, part Dachshund, part Yorkie. I love him sooo much, he's really smart and such a momma's boy. He's 15 month old. The first part of housebreaking was such a pain, but when he finally started getting it he was great. Now he always asks to go outside to pee and hasn't gone inside for months. However poop is such a different story. I know his schedule, he poops in the morning before I leave for work and once when I get home from work. I always take him out when I get home from anywhere and I always ask him if he has to poop any time we go outside, but I can spend forever outside with him and he seldom goes, but a couple mins after we come inside he sneaks into the kitchen and poops on my floor. He rarely will go outside, but if i follow him around he wont go, it's almost as if he's too shy (if that's even possible) I scold him every time I catch him and he gets all moppy all apologetic looking, but still does it . . . I've even started picking up the poop and taking him and it outside together. I live in an apartment and it's not like i can let him out by himself or even close off my kitchen too him. Any suggestions?