I agree you're already on the right track because you're aware that you're doing it. Can you challenge those thoughts as they come up? Maybe try writing them down and then writing a positive alternative thought.

I find I have easier time changing my negative thought patterns when I have a consistent gratitude practice going. Right now I've got a Gratitude Rock (google this for info) which might seem cheesy, but it is helping me. Worth checking out.

I hope you get out of this rough patch soon.