Enforcement for council tax

[Qwertyuiop]

Hi,I have been living with my ex husband in a property which he was on the contract for rent and council tax bill,I was just giving him half of the money every month.we were separated and going through divorce at that time.just found out that he stop.paying council tax bill from last april,without me knowing.i moved out from him in November last year.strange thing is my twin sister which she lives in different town recieved letter addressed to my name that I have enforcement bill for council tax.he obviously put me on the bill,I didnt recieved any letters addressed to me as he locked the letter box and he was giving me any post to me if I had.i m 7 months pregnant and have high risk pregnancy now I m stressed so much,dont know what to do.