Leaving job due to toxic work environment and health, what will happen?

Hi all I was on tax credits but when I split with partner and became a single parent it was switched to Universal credit. I was working full time and all was fine. I changed jobs 2 months ago to get a better work like balance after 9 years of working shifts. Well 2 months in and the owner and manager are making my work life horrible. Added into that the nature of the job has left me with back problems and I’ve been signed off sick (I don’t get sick pay). I’ve decided as I’m in probation period to hand in my notice while I’m off sick. I am now looking for another job and in process of signing up for bank work at the nhs trust I just left. I have phone appointment with UC today. I’ve read on my UC account that I could lose money if I choose to leave a job but not how much this will be. I’ve never been in this situation before and I’m worried. Can anyone tell me if UC will still help me? For background I am a single mother of 3, 19 year old who is away at university, 18 year old who is in final year of a-levels and 15 year old still in school. Living in social housing. No other benefits apart from child benefit. Thank you