Help! Iphone won't sync to itunes after music transfer from computer!

I have an iphone 4. Recently I tried to add music files from my computer's library to my itunes library. However when I transferred my computer music files to my itunes account, it asked me for my itunes account password. I typed in my password, but since then I haven't been able to sync my iphone to my itunes account. I think I remember something saying that it was bringing music from another account and it asked if I want to do that, then I said yes, but I amvery confused on why it won't connect. Why did this happen?