Apart from posting a verse, which would help, could you say which tune you had thought of adapting? Then those who are reading this might be able to say if it was an over-used tune or not.
I can think of several tunes that HAVE been repeatedly used for different songs, e.g. Star of the County Down, Tramps and Hawkers, Puir Roving Lassie, Nicky Tams, Sick Note. (Just citing one example for each tune here, not listing all the respective songs.) So best avoid any of those tunes.