Dear Mizmija,
If you face with the side effects of Finasteride you can try to slow down your hair loss and your hair thinning by alternative non surgical treatments such as PRP and Derma roller+Mesotherapy. Although PRP is not FDA approved for hair regrowth, in lots of cases we are seeing significant result at the end of 4 PRP sessions.
You can maintain your current situation by PRP and Dermaroller(Mesotherapy) until your 25-26. By doing so you will also maintain the strength of your current donor area.
If you will face with NW 6 or 7 in future, you should proceed with FUT or a combination of FUT&FUE. In FUT hair transplant it is possible to collect and transplant more number of grafts compare to FUE.
I hope it was helpful. If you have further questions please do not hesitate to ask.
Best regards,