I-864 or I-864A with husband.

[princessbpn]

I applied for my mom's GC and was the sole sponsor for I-864 because I made enough money to be the sponsor. However since the application was made my circumstances have changed and I am now working part-time and going to school full time. My husband is willing to help in this case.
However I am not entirely sure if he should be a co-sponsor with me or should he fill out I-864A?
The application is still in process because we had to wait to get certain documents for my mother. I have them and will be sending them in a few days along with the proper I-864 or I-864A form.
TIA

[newacct]

First, the Affidavit of Support you filed is still valid because it was correct as of the time you signed and filed it. If there is an interview they will likely ask you whether you are still at the same job, and if not ask you for a new Affidavit of Support. If there is no interview then you won't have to do anything.

If you need to file a new Affidavit of Support, your husband should act as your household member, and not act as a joint sponsor. So he would fill out I-864A and his income would be counted in your household income on your I-864.