Problem logging in

I created an OSM account a year ago but I had not contributed to OSM using that account. A few days before, I created a new account ( as I had forgotten that I had an existing OSM account) using the same reference email that I had used to make my first OSM account. OSM accepted the same email account and I continued to contribute to HOT'S Tasking Manager using the newly created account. But now, I am having a problem with my newly created OSM account while logging in as OSM recognizes my old OSM username instead of the new one. Even if I use my old OSM account instead of the new one, all the progress that I made in my new account will not be reflected on my old account. Is there anything that I can do to log in into my new OSM account? Can u help me?