You would need to do a new I&E to show the up to date position. He would almost certainly be contributing towards the running costs of the property so this may mean your payments would increase.
You can either allocate your living expenses in a 50/50 ratio, or in line with your individual earnings. So as Michael says this reallocation of costs may well leave you with more surplus disposable income, and therefore able to increase your payments into the IVA. Seek direct advice from your own IP on this point, who has detailed knowledge of your case.
