Metronome or drum machine or other means to improve your timing is a must, so you are on the right track.

Timing is the most important aspect of music. Without timing there is no music, there is only sound. I'd rather play with a beginner with good timing than a virtuoso who doesn't.

Metronome, drum machine, all good. I've recently purchased PC Drummer (About $40), which is software I can write drum tracks with. Since you are writing, you might want to consider something like that to help both your songs and your timing.