Are you passing any gas? If not it's doctor visit time.
If you can fart okay and you are not aware of any particular, um, buildup, it might just be that you are taking in next to nothing by mouth, so there's hardly any waste to get rid of.
If you are aware of stuff that isn't moving, then there are lots of things you can take. Miralax, Colace (docusate sodium), prune juice, a Fleet enema, a glycerin suppository....Just don't take a stimulant laxative without your doc's express direction.
And when in doubt CALL THE DOC. It's much better call too often than not often enough. You won't necessarily speak to Dr. Gagner about all this stuff, but there are qualified people around who can talk about it.