in your shoes, I would stay in UK and join your husband only after a few months. Let him settle before into his job and life in Doha whilst you have your family support back home. You can always join him in October when the weather is starting to cool down and hopefully by then, if you are being treated and looked after, your depression will be a thing of the past and you'll be ready for the challenge of moving to Qatar.

I wish you the best.