It's good that you feel bad about it. Don't think because you slipped up, that it's ok. I may sound harsh, but Paji its this discipline that is going to help you. You have to not feel sorry for yourself, but admit to God that you messed up and don't hide what you have done, ask for forgiveness from God, not from us or anybody else, as we won't be there when the going gets tough. I understand you are feeling lonely, but that's no excuse to drink or take drugs. The whole world is lonely, nobody belongs to anybody. Nobody will be there for you in bad times, believe me I should know. You should not feel lonely, as you have a good job, you are in this country which offers so much. I've just been to India, and compared to being there, you are in the best place now. Just imagine if you were there, how would you cope. It's no swarg there, probably living hell, if somebody goes through alcohol and drugs problem there.
You are very lucky to be born in this country, so don't take it for granted, respect what you have, even if it doesn't feel much.
Every soul is here because of their past karam and to jap Naam. You feel lonely now, then what will you feel when the damage of intoxicants will take over your life? God forbid that ever happens, but I know from experience, a member of my family used to drink, I think I told you about it too. And it was very hard to see what they were going through, which also affected tho whole family badly.
Take a grip of yourself, and get up now that you have fallen. You need to respect your soul more, stop hurting it, God gave you it to love yourself and to clean your soul through good actions. Enough is enough now, amli na ban, Kuch nai rakhea is cheeja vich.
If you are depressed, get professional help. MisterrSingh Paji is right, your cousins will get married, have kids, and they won't be there for you. They won't give a c r a p about you and it's your family who will get the mehne, so why are you giving them the chance for that?
Not eating isn't going to make things better, but worse, you have to keep your strength up to live, and to clear your mind from negativity, guide it to goodness. You have to not want to drink yourself, it's got to come from inside you. No matter what we say on here, doesn't make a difference, unless from deep inside your soul you are ready for that change.
You think temptation is easy to control, but you got to be harder with your Mann (mind). If one give the Mann is bit of freedom, then it will run like a horse into hell. Hold onto the reigns, otherwise you are going to hurt yourself more, after falling off.
And what the hell you doing near pubs, obviously you will get tempted. Keep away from pubs, that will help you.