Terrified.... I don't want to do this

Recently my boyfriend of three years the love of my life and the father of my kids had started taking Xanax "because he's depressed and has anxiety he feels alone and the Xanax makes him happy" things have been getting worse and he's been high on Xanax for three days straight I don't even recognize who he's becoming I am watching the person I love turn into a complete stranger and it's killing me he says we are important to him and he cares about us but he refuses to go to a doctor to get help because "he doesn't want to be doped up on pills and he doesn't need help" he also said "I love you guys I care about you guys you are the most important things to me but I can't quit taking them for you" and I'm lost I'm hurt I don't know what to do why are we not important enough for him to stop if he doesn't care about me and I'm not important then fine but why is our son not important enough why is our unborn baby not important enough I've been crying for three days devastated and hurt I don't want to be a single mom I don't want to be a single mom of two kids a toddler and a newborn (I'm due in March) I love him so much and I don't want to lose him but I know I'm being selfish because my kids don't deserve to grow up with a dad who's high on Xanax all the time who refuses to get help.... I'm so lost and my heart is shattered

****UPDATE**** I don't know if anyone cares but I stayed up last night crying my eyes out and I contacted his sister and told her EVERYTHING there's too much to say on here but she said "I have to tell my dad this is serious and not an issue we can just hide and keep secret what if he got so high and did kill himself or hurt you guys I'm sorry but I need to tell my dad" and I was scared honestly scared I didn't want my boyfriend to hate me for telling his family but she also messaged their niece (their niece is older then my boyfriend and one year older then his sister) well his niece messaged him asking him if he was ok and told him he needs to seek help his dad also messaged him telling him he needed to go seek professional help and said he wanted to come talk to him and check on him my boyfriend then came to me after telling me what they said and asked me "am I really that fucked up is it really that obvious" and I said "yes it is that obvious you don't see it because you're high and your friend isn't going to tell you you have a problem because you buy them from him but you are depressed and masking it or trying to mask it with Xanax isn't helping you seem brain dead when you're high" and he started crying and said "my dad wants me to get help so I'm going to get help everyone is telling me I need help" so I felt relief he was finally agreeing to get himself some mental help and to get off the Xanax it was finally like I was getting somewhere to help him but then his friend who he gets the Xanax from came over (his friend also takes Xanax) and my boyfriend was talking about his feelings and I guess he started crying so his friend gave him a Xanax and they both took one and I guess after they took it they did a "bro shake" and agreed and promised that today was the last day that they were going to take Xanax and that they are done with them I of course cried on and off all day again because for the past 3 days or longer I've been crying begging him to get help for his mental health begging him to stop taking the Xanax asking why we weren't important enough for him to stop and I have just been emotionally exhausted and crying so much yesterday he said "you guys are important to me I care about you guys and I love you guys but I cant quit for you guys" but he can quit for his fuckin friend I just don't understand it I can see he agreed to get help because of his dad because he's always so scared to disappoint his dad and he holds what his dad thinks of him to a high value and standard but he can quit for his friend but not us that honestly hurts so much

Now it's day four of crying on and off FOUR straight days I've cried and begged him to stop four days I've been hurt over and over again I honestly can feel my heart breaking and it's killing me what have I done so wrong why am I not important why are our kids not important why doesn't he seem to care about us