My new dog hasn't pooped all day - should I be worried?

Ok I know this topic comes up a lot and I've read a lot of the poop threads here in this section, have even written down notes, but I still cannot get my new 3 year old dog Rascal to POOP!!!!! AHHHH It's 9:00 pm here, I'm ready to go to bed I"m so tired but he hasn't been all day.. [:(] He does fine with urinating all over the bushes outside, but he won't do the other

He's 15 lbs., needs to lose a little weight, gets 1 cup of his dry doggy food (1/2 in the morning, 1/2 in the afternoon), plus various treats for good behavior (I don't give them to him for no reason).

On Thursday (his first day) he pooped inside the house, Friday he did it again when I slipped away to take a quick shower. Since then I've had him on leash and by my side all day. Yesterday he did it after running around in the park, then again about 2 minutes later (whoo hoo). It was about 45 minutes after his afternoon 1/2 cup of food. Today - NOTHING!

He's gotten lots of exercise, we took a long walk and played with his ball and I"ve walked him around everwhere outside countless times hoping he'd find a place he wants to go, but he just won't go! He even gives me signals inside, like sniffing everywhere, and he looked like he had his tail between his legs and was trying to hold it in so I ran him out...and nothing.

He doesn't seem distressed about not going but I AM!!!!!! It can't be normal?? could he be constipated or still nerves from moving into a new home?? I have a crate for him that he slept in today for about 2 hours as practice for tomorrow (when he'll need to be in it for 3 hours while I'm away) and he did great besides a little whining before he fell asleep..should I put him in the crate tonight or let him just have an accident if he needs to go? I've been letting him sleep in his bed in the living room at night and he's done great the past 2 nights with not going potty when I'm asleep ..

sorry this is so long. absolutely ANY thoughts would be much appreciated