What does Judaism say about therapy and mental health? Is it a lack of faith to need it?

I wish this question did not still need to be asked, but I am glad you asked it. There is no contradiction between emunah and therapy. The Rambam was a physician; our tradition has always honored healing as holy work. Faith can give you meaning and a frame; it is not a substitute for treating depression, anxiety, or trauma, any more than tehillim is a substitute for insulin.

In practice they help each other. A good therapist can lift the weight enough that your davening feels like yours again instead of a chore you drag yourself through. Find a competent professional — ideally one who respects your world — and treat going as the mitzvah of caring for yourself that it is.