Do you think guitar lessons would be a good idea?

I've been teaching myself how to play the guitar for around 6 months now, and I've made quite good progress. I can play most songs that I want to and I can play barre/bar chords without too many problems, but I feel like I'm not really getting anywhere anymore, I feel like I'm not improving as much as I was, and I think I might benefit from getting a teacher. I haven't really learned much of the 'theory' side of things, and can only read chords and tabs at the moment. Do you think I should get a guitar teacher or would it be a waste of time/money?