You don't need to register your track with a PRO if you got forwarded to a publisher or library. If they sign your track, THEY will register it with you as the writer and themselves as the publisher anyway. If they re-title, that registration will be under the alternate title.
If you are marketing a track directly to end users with you taking both the writer's and publisher's share, then you should register it yourself. Also, if you place the track in a library that does not share in PRO royalties-- there are a few
(not many) that only share in up-front license fees, then you should register it.
Note that some libraries register all tracks they sign within a few weeks or months (sometimes longer) of signing. Others don't bother registering unless there is serious interest or a placement.