Im at my wits end,my son is 27 and for the last eight, nine, years,hes been in and out of hospital,?

hes been diagnosed with bipolar,scitzophinia,depression,multiple personaliy disorder,my partner and i have been there for him allways,sorting him out,living with us until he got back on track with his meds,hes had his own places half a dozen times and weve been there for him ,decorating,sorting furniture for him,being a taxi,genrally cleaning his mess up behind him,then he will start drinking,this will then lead to wot ever drug at the time he fancies,heroin,coke,bubble,speed is the lastest one,when hes taking his meds hes fine,but he thinks he knows better than even the doctors,so theres no talking to him,ive been trying to talk him into going into rehab,but wots the point,he dosent admit hes got a prob,my partner now says ive been running round behind him that long that hes not going to change,he just expects it all the time,recently ive been saying no to him hoping that he might stand on his own two feet,and take some responsibility for his own actions,instead of blaming everyone else,he is the middle child hes got 2 brothers who have partners,children.and decent jobs,he was in a relationship for just over 3 years till it ended he was 22,and she did get pregnant within weeks of splitting with him,so that dident help his frame of mind as he did want a child with her,but hes been going dowhill ever since,nobody seems to be able to put up with him any more,his dad, brothers,gran n grandad,aunts,everyones fed up of his behaviour,from scrounging money,taking what ever he wants,talking in riddles,his dad has alcohol problems,he has tried at times with him,i cant have him living with me anymore as he drives me mad after a few weeks,but hes good at manipulating,and making me feel guilty,because i left his dad.he was 17 at the time,people say you have to be cruel to be kind sometimes,but im not good at this,because hes my son at the end of the day and i love him to bits,but i love my partner and dont want to loose either of them,and im afraid i might if something dosent change,thankyou if anyone answers,sorry about spelling mistakes,