I always get a decent job normally in construction but after a few months the sick days add up and I get fired then usually find another job straight after I suffer from bad deppresion so I drink a lot and once I start drinking it's hard to stop and I become vile and nasty I need to ease up on it all but I find It hard to cope with reality everytime I get something going for me I fuck it up
honestly it sounds more like your underlying mental health problems are causing your difficulties rather than your drinking, as you see this as caused by your depression. it says you're in the UK so i know that right now unless you are basically suicidal your chances of getting help on the NHS is very small. still, go to your GP, its possible medication could help and you could get a referral, even if you have to wait ages.
i personally find that not working massively exacerbates mental health problems, but then they make work almost impossible. that said, the two most intensive periods of mental illness in my life were due to having nothing to do. one time my uni had told me i didn't have to sit any exams or basically do anything cos of the situation i was in at the time, the other i lost my job through crack usage.
that said, sometimes you do actually need a time out of work to just work on yourself. but then that needs to take priority. see what help is available near you, try your drug and alcohol services- even if you don't think you need it, i didn't think i did but they really helped me and i didn't need to wait for a referral to start using their resources.
try AA/NA/whatever peer support, even if you don't think you're an addict, its causing you problems and if you don't tackle them, they tend to get worse. i WISH i had done this when i was just turning up late cos i was using gear and sometimes needing a long lunch break to score as i'd not had enough in the morning to hold me. much better than doing it after i'd lost an amazing job due to basically never turning up and even if i was physically in the office i'd disappear for hours at a time to use and did no work.
i honestly reckon if you try and work on the depression, the rest should improve. what have you tried?
also, my first real job considered more than 2 instances of sickness in a 6 month period a disciplinary issue. it put the fear of god into me, i still get anxiety about having to call in sick. it was a shitty policy but i think that attitude has helped me. i have to work a lot of days very hungover, and often consider calling in, sometimes i get fuck all done in those days. sometimes i surprise myself. also, it gives you something to do. mental illness feeds off empty time.