I will start by saying that NOBODY should be in pain! Study after study shows that patients are undermedicated for pain in this country. This is often due to concerns about getting addicted - which is not particularly common, especially for drugs given to combat side effects of chemo.
One common side effect of oxaliplatin is that it effects the bone marrow, which can cause bone pain as well as other issues (for instance, increased risk of infections). So this is not all that uncommon, but absolutely SHOULD be treated with the appropriate pain medication. If a regular painkiller (tylenol or whatever) isn't working, there are some drugs that work specifically for bone pain. Ask your husband's doc and get him on one.
I would also ask for a PET scan if he hasn't had one - yes, the CT and MRI might not have shown anything, but a PET scan might. You might have to fight for this, as it is usually a follow-up to a suspicious CT scan. You also might be able to ask for the combination PET/CT, which is much more effective (I think about 11-12% if I remember correctly) in picking up metastases early.
Abby (and anyone else hearing this from a doc), if any doctor is telling you or your husband that he is "maxed out" on pain killers, GET A NEW DOCTOR or at the very least, ask for a referral to a pain specialist. Although it may take a little time to find the right combination of drugs that works for your husband, here is ALWAYS something that can be used, and you really can't max out on much of anything.
Hannah