Hi I came to this website before when I started getting interested in game design and such, but I became busy and left. I am now working on making some music of my own via Forte Standard. I have some songs I think are good (mainly one), but I don't know how to find out if it violates copyright or not. Does anyone know how I can find out if my ideas have already been used or not?

There is no practical way to do what you want. However, providing you didn't deliberately set out to copy someone else, if you are writing your own music then the chance of you infringing copyright is close to zero.

As far as I know, it is possible to infringe your publisher's authoral rights by using material you've provided the, IIRC that could be classified as self-plagiarism. Aside from that, I don't see why not.