Behaviour and temper

Can anybody give me advice, my daughter is 6 she has asd diagnosis less than a year ago, lately her behaviour has got really bad at home mostly just verbal and unbelievably disobediant, today i lost my temper and screamed at her at the top of my voice she was scared of me and now im worried its not going to get any better, is there any proffessional help like behaviour therapy or something i should be doing i also have a 9 month old baby so i feel so guilty i cant give her all my attention. What should i be doing for her??? I feel like im failing and that she isnt happy with me as a mother and that why she acts up for me.

Any advice is greatly appreciated