In a healthy relationship, this wouldn't be an issue. I suspect that the inheritance isn't making you fight; the quality of your relationship is making you fight.

The best advice I've heard for equalizing financial inequality in a relationship is pretty straight forward: pay a percentage of the household expenses based on your income. If he makes twice what you do, he pays 66.5% of the total and you pay 33.5%. That way each of you is contributing an equal percentage of your income, even though the dollar amount is not equal.

But you might also want to ask yourself if your generosity prior to his inheritance was as self-less as you make it sound. Are you sure you are not angry because he's not returning the favor? If so, you didn't do it for the right reasons in the first place.

Another question you might consider: Could he have been with you in part because he needed financial security. Is it possible that now that he doesn't, he's questioning your value?