There are various ways to test and break hexes, but unless he messed with someone he shouldn't have, it's unlikely to be a hex or curse. They take a lot of energy and are unlikely to be cast unless you severely anger someone. Assuming this is a medical issue, the best first step would be to see a medical professional, as modern medicine should always come before magical alternatives. Chances are, it's non-magic related and needs to be checked out.
Otherwise, if you know what ingredients were used in the hex, you can use the same ones to perform a counter. If you don't, I'd suggest cleansing and warding your house to prevent anything new from being placed onto you or your husband, then cleansing your husband himself via either salt, smoke, water, or some other method you prefer. This should help reverse the hex. If not, it may be something stronger (a curse) and will therefore take more effort to break. If you'd like some form of "test" to ensure whether he is hexed or that the hex is broken, asking your deity and performing a preferred method of divination can help.