So, you've not smoked for six months? That's good as nicotine causes arteries to narrow, the opposite of what's useful.
It's well enough known that using c-rings can be risky, and -- a meth I.V. user, too. Well, there certainly might have been some damage, hopefully reversible with time. As to being assessed, there's so much variance between patients that only change (between earlier and now) as comparable by before and after photographs, would have much meaning to a doctor or urologist, in the absence of recorded measurements at physical checkups, unless there's something blatant like lack of function or gross visible to anyone defect. Doctors deal in disease, something not working, and so far, you're still functional, albeit at a lower level by your estimate.
My suggestion: keep a careful record of any measurements, store private photos. With the intent of repeating this every three or six months indefinitely to be able to look back and do close comparisons, until you've a better handle on the situation (improving, worsening, staying the same).
It is Change, that you now want and need to track reliably.
Well done on being drug and alcohol free for 6 months. That can't have been easy for you.
Anti-psychotic drugs can cause some genital shrinkage and this is not fully reversible when you discontinue the medication. So in a sense, physically, what you have got down there is what you have got. Stop measuring it and stop fretting about it. Its fine.
Now on the functionality side you have got yourself tied up in knots from obsessing and watching yourself. Once you are in the audience looking at yourself trying to perform you are doomed to failure. Take intercourse off the menu for a while. Tell that new girlfriend that you are doing off duty and that she can do all the work. Learn to laugh at yourself and have fun. This will all come right as soon as you get out of the space you are in at the moment.
And by the way, don't expect too much from the urologist. You are only being sent to him because the GP did not know what else to do with you.
6.5 inch length of erect penis is normal. Vagina is sexually sensitive up to 2 inch depth only. So 2 inch erect penis can satisfy his partner. Kegel exercise is good. You should do it for longer period to get the result. Anal peripheral prostate massage is better than kegel. you can also do male deer exercise. Self measurment of penis is usually wrong. It is measured with great care. So do not bother to measure your penis. length is okay. If it has retracted it will come out with the massage of coconut oil.Use virgin coconut oil. Do not laugh at this suggestion. Do it. for a week. You can learn kundalini yoga to enhance your sexual strength. It is a long term process. If you learn and do it seriously, you can change your overall life. wish you best of luck.