Is this weird (question about piano playing esp. in the left hand)?

Okay i am a right handed piano player and have a weird problem about improvising / song writing on the piano. Like I play the notes very well i think and come up with some pretty creative notes and even progressions or whatnot. But i have a problem with trying to make the rhythm and such. Like you know how songs play like an eighth note in the treble clef and then a quarter note, and they play like a half note in the bass? I have a problem cause i get attached to playing chords and starting the melody at the same time as the harmony, and is there any way that i can quit this? Like i want to be able to play single notes down there but i have trouble with the timing, especially in the left hand.. Are there like any exercises for the left hand that i could use to open my brain up to being more creative in the left hand or anything? Thanks (: