I paid all the bills for 3 months when we split up

There is no rule or law that says the breadwinner is obligated to pay 3 or any number of months of household bills. However it is common that upon an application for interim spousal support following a separation, the higher income earner will be ordered to pay spousal support to the lower income earner – the amount being based on the difference in the parties incomes and the length of the cohabitation according to the Spousal Support Guidelines. The next step for you would be to either negotiate a reasonable amount of spousal and child support in accordance with the ranges and durations provided for in the Guidelines or to go to court to resolve those issues. If you are bearing a disproportionate amount of the family debt, that debt payment can be used to offset and reduce either the child support (under the Undue Hardship Provisions of the Child Support Guidelines) or can be used as a form of third party payment of spousal support to reduce the support otherwise payable to your spouse and to allow you to claim her share of the debt (being paid on her behalf by you under a third party spousal support payment order) as a tax deductible spousal support payment being made by you. In order to be deductible under the Income Tax Act, the arrangement must be pursuant to a court order for spousal support or a written agreement (which includes terms confirm that you get to deduct the payments and that she will declare those payments as income.