Firstly, try not to consider yourself a burden and don't blame yourself for your depression. Admitting it, even here is the first step to feeling better.
Next, is there an external cause for how you feel that you can pin down. If not how are you health wise. How well controlled is your diabetes. Is there a pattern to when you feel down, Sorry for all the questions but finding out why you feel as you do is half the battle. It could be a result of blood sugar fluctuations, or hormonal. If something specific is worrying you then it can affect your lack of sleep which will make you feel worse.
If you can try and talk to your doctor or nurse about it, they might be able to get you on a talking therapy course, waiting time can be long but you might be lucky. They can also test if there is any medical reason for the depression. Don't just accept a handful of tablets, that can just make you feel worse, you need to get to the cause of the problem.
Hope you feel better soon.