I'm still grinding/clenching my teeth!

My theory is that the clenching it induced threw off my bite and now because my bite is screwed up I'm clenching all the time. The clenching grinding happens mostly at night while I'm asleep, and then in the daytime my mouth hurts all day.

How can I correct this?? I saw a dentist and he said it was due to stress and to calm down, but I really don't think it is. He gave me a mouth guard but it doesn't seem to help.