Let me clarify in the beginning, any form of substance abuse
is bad for your health, and worst is IV drug abuse
. you should stop is as early as possible and seek professional help for it.
The symptoms you describe can be be because of the overdose of drug.
Another possibility is due to repeated use of the vein the vein gets thrombosis
and its a fare chance that you dislodged a clot which caused the above episode. Even if you change veins you are going to face the the same problem and can be dangerous to your life.
I would again like to emphasize you stop using drug abuse and that is the cure for you.
Hope it helped. Feel free to ask any more queries. Take care and be substance free.