I've come to realize my timing is not rock solid. What can I do to improve? Background:

Self-taught basically (took lessons for about a year and a half too), been playing in bands for 12 years, nothing very serious, but I've played out at bars and stuff. Original music. I'm having trouble setting a tempo and sticking with it throughout as we move from verse to chorus. It's usually close, but I tend to both speed up AND slow down within the song. Of course, now that it's been pointed out, my confidence is shot so I'm second guessing myself, making it worse in some cases. 

In the past, working with a metronome has just served to frustrate  the hell out of me. I can't tell if I'm going faster or slower than the beep and can only follow it at very slow speeds. Any advice on working with one (since that's probably what I need) or advice on other exercises that might help? Thanks.