Boyfriend drinking to much :/

My boyfriend of three years father of my daughter and soon to be a father again to another daughter of mine.. A few weeks ago I found out he was texting my step sister and hitting on her when I told him I knew about it he felt really bad and said he fucked up and he was drinking and thinks the reason he's done what he has was because he's never had freedom to do what he wants and he would do anything to fix.. Since then he's started drinking A lot pretty much everyday. We are constantly fighting because when he gets drinking he just says whatever doesn't care if he hurts me by saying what he does. I have told him how I feel about him drinking and I honestly love this man he's been my best friend for 10 years been together for 3 been in love with him for 5 years. I don't wanna just give up on our relationship I do love him but seems like things keep getting worse and worse it seems ic told him I feel like he has to be drinking in order to be around me and he has also told me he don't intend to stop drinking that it makes him feel better. I honestly don't know how to deal with this :'( I've been soo stressed out the last few week this is not the life I want for my babies I grew up with an alcoholic father and he says he wants a better life for his children then he had but I don't see how this is better :( im so lost I love this man I really do and I don't wanna lose him but I feel like I am losing him :'(