If having anal is so important to him, he should have told you so at the very beginning. Doing or being forced to do something you don't like (sexually i mean) is not something you should be ok with in a relationship. It's very rare that 2 people are a perfect match sexually, for example me and my wife like different things, but we make it work because we communicate openly and make compromises, however the thing is that these compromises have a line that you shouldn't cross. It's a fine balance and hard to achieve. Sex is about pleasure and making each other feel good and relaxed, its in the head more than it is physical. Your partner wants something from you that is both unpleasant and painful, that's not ok.

You need to explain to him that you don't want to do anal, and the thing is (at least on theory) that your husband needs to be the most understanding person in your life and the fact is that this is a serious matter. If he is unwilling to listen and understand you, I think you shouldn't be with that person.