After Rhinoplasty I've Been Really Depressed, Is it Possible to Reverse Surgery?

I'm sorry you are feeling depressed, but as mentioned, such feelings can be normal after surgery, especially on such a cosmetically sensitive area as the face.  But you should be reassured that if there is a result you are unhappy with, it can be improved.  Adding cartilage or other grafts can correct an excessively reduced dorsum.  Keep your appointments with your surgeon and express your concerns.  

Depression or feelings of regret are not common after well planned cosmetic surgery, though if you are very troubled with your decision you should speak to your surgeon about it. It is possible to get some of the essence of your old nose back but it might be better to wait and talk things through with a professional, if necessary, so regrets don't compound. Remember, our outside largely reflects what is within, as cosmetic surgery really has not changed who you are.
Best of luck, peterejohnsonmd.com

What you are describing is not unusual. Discuss this with your plastic surgeon and perhaps your primary care doctor as some counseling may help. While reversing a rhinoplasty is possible, it is not the thing to do and unlikely to restore your old appearance. Most likely, it will take some time for you to accept, and enjoy, your new nose.