Hi! You have not mentioned whether you were taking oral drugs or injectable drugs. In the second case, whether you had your own syringes or you shared the syringes with any of your friends. If you were using IV drugs, and were a self help type, possibly you were injecting yourself in your left arm/forearm veins in case you are a right handed person. It is a possibility that you might have injured your nerves in the arm or have developed vacular (specially venous) pathology in your arm which might be manifesting as weakness in your left arm.
On your abdominal discomfort, I would advise you to go for an unltrasound abdomen and blood tests like Hb%, C, TLC
, LFT, Tests for Hepatitis B
and C antigen, along with a HIV test
on advice of your treating doctor/counsellor.
You have to overcome your stress
by your will power. If you could leave your drug habits for 3 yrs, then you have got enough will power to overcome your stress as well. Go for regular exercises like morning walk, jogging, and eat a lot of vegetables and liquids and meditate if it suits you.If the stress level increases however, you should consult your Psyciatrist/Counsellor. I hope this helps you somewhat.