"Si tu sintieras lo mismo que yo, estuvieras aqui conmigo" (If you felt the same as me, you'd be here with me)
Now of course, the way I learned it in school, the second part should read "estarias aqui conmigo," but the construct as it appears in the song seems to be more common than the one I learned, as I hear it nearly everyday and it's rare for me to hear the other one.
As a matter of fact, the other day I was speaking to a coworker, and I said something using the construct with the conditional, and she didn't understand me at first. Is it becoming that rare?? Any help is appreciated, so I know whether or not I can just drop the conditional tense in sentences like this altogether. Les agradezco mucho su ayuda.