Oh, I do sympathize - I've been plagued with all kinds of sinus and catarrh problems since I was a kid, but was lucky enough to find a classical singing teacher who stopped me from constant throat-clearing. Once you've got a medical assessment of the damage and started to find ways to repair it, then it's worth finding other ways to clear your throat rather than half-coughing and so scraping away at the vocal cords - you could try to work up some saliva and swallow it . Or you could eat boiled sweets (not necessarily the mentholated variety) just prior to singing. It also might be worth having a bash at finding an Alexander Technique vocal coach to help with correct posture, etc, which also helped me find ways to sing through that awful blocked feeling.