tambdy. Firstly, look in the mirror. Is your skin yellow? It would be if you were in end-stage liver disease, although, jaundice (yellow skin) is not a definite indictator that you are, the absence of yellow skin means that you are not. Have a look at the whites of your eyes, are they yellow? That indicates that you have some liver problems, if they are, but the liver is very good at repairing itself if the alcohol or drugs which are causing the problem are removed from your life.
You say that you are in your 20s. From alcohol alone, you would have had to drink absolutely massive amounts to ruin your liver, I am talking two 1 litre bottles of spirits a day for a few years. Yes, you would kill yourself young if you carried on drinking for years, and it is very bad to get into a habit where you can't stop without suffering severe withdrawal symptoms.
I think it is likely that, if your liver was in a very poor condition, your doctor would have recognised that instantly. I don't know you and I haven't seen you but I would hazard a guess that you are panicking when you don't need to 
Go back to your doctor and ask him/her to do tests. If you want reassurance regarding your liver, ask the doctor to do Liver Function Tests (LFTs) which consist of a blood test which is sent off to the lab and you get the results a few days later.
The most important thing is that you have stopped drinking. I don't know how much you were drinking but I guess it was a lot if you are now worried.
Try not to worry too much, the pains could be many things, most of which are not serious, but you need to be properly examined and for the doctor to know that you are now having worse pain on your left side.
Your biggest fear, that you may be dying, seems very unlikely to me, even with the small amount of information you have given, but you must go back to the doctor because most illnesses can be more effectively treated the earlier they are diagnosed.
I hope you get it resolved quickly 