You obviously don't like the situations you are into, and I 'll admit that is really doesn't sound like you're living a dream life,
BUT it's not entirely bad if you think this is not the dead end and as a 27 years old healthy young man you still have all the time in the world to turn it all around.
It might sound like I'm making things easy but life ends when it ends ....until then, there is time to change it if you don't like it, it's just hard, but definitely not impossible, so don't think there is nothing you can do to get yourself in a better situation because there is, ... the thing you have to ask yourself is how much you want to get out of there and how much strenght you are ready to invest in your "escape" .
Some people let themselves "die" because they think they do not have what it takes to change things, and while there really are people who don't have that kind of strenght, you sure look like someone who has it.
Your posts indirectly say that you already have what it takes, a certain ammount of different personal skills that you are probably not giving the right weight to.
1 to get a job and not getting fired from it means you have endurance and a pretty high sense of responsablity ( it also means that despite not liking something ( your job ) you are still ready to face it everyday for the sake of obtaining a profit out of it ( money ). ( doesn't matter if you eventually took one day off )
2 Having friends and a girlfriend means that you have ( or had anyway ) at some point in your life the necessary social skills to draw people to you and make them like you.
3 Taking satisfaction in helping other people and thinking of it as something worthy gives away that you luckily have good heart and a great empathy, and the fact that you refer to it as " the happiest point of the day" also means that you are a deep person who naturally gives priority to said type of gratifications rather than more shallow ones.
4 The fact that it "irks" you to see you parents doing nothing and living every day as if it was the same instead, it's a sign that any type of self destructing behavior,even the less serious cases such as apathy or resignation are naturally and instinctively rejected by your conscience (at least subconsciously), and that is proof that you are someone who, for his nature not only hates the idea of people destroying their life with thier own hands, but also dislikes the idea of them simply surviving instead of choosing to" live ".
I think you are someone who's naturally ( even though probably unsconciously ) very prone to "live" in the real sense of the word, fully and completely, and has all it takes to do it, but has just been discouraged by not seeing the same will in the people around and eventually as the years passed settled to follow their wrong example leading a mediocre life .
I personally think you can't sleep at night because deep inside of you you're afraid to end up like your parents, carrying on and surviving this worthless way until you're old and there will be nothing left to do for you except to look back and feel regretful to have lived an empty life.
But you don't have to worry the very same fact you fear it so much you can't sleep in peace, it's proof you will not end that way, see ? your subconcious is already rebelling to that idea.
All that is left for you to do is to do it consciently too.
You are currently unsatisfied with you life so go ahead and try to change things as much as you can : Will to live, endurance, wisdom at ayoung age, a very strong coscience... are all things that you luckily already possess and could easily help you out of the hole you unwillingly dug yourself into during these empty years.
Sit down grab a pen and make a plan, think about what you really want to do, or how you you want to end up like when you'll be 50 and try to think of how you can achive it from where you are now. ( Sounds tough huh ? but it helps to clear you mind and set objectives )
In the mean while as a side activity ( since helping others make you feel more realized ) I might suggest you to take part in a charitable organization ... there you can do what you seem to consider " worthy " and make some nice good hearted friends at the same time, talk about it to you girlfriend and join together... it might help you. If there isn't any around you try looking online or go to the nearest church I think any priest would be more than glad to help you find one.
PS
Don't start smoking, quitting ain't easy and the only think you can get from it is cancer, not stress relief.
Stop drinking that much,only idiots get drunk and you don't sound like one, start to drink less and less every day and that problem will fade away, it seems obvious to me that you drink to forget and feel better, but the same effect can be achived through other healthier solutions, go to your doctor and tell him what you have, he will give you sleeping pills or a light anti depressive that will make you feel much better than alchool, I'm trying some and it works.
I wish you the best
PPS
But in the end if I had to give you only 1 advice I would tell you this : read the Gospel, the message Jesus left to us and believe in it... it saved me and it's still doing it.