Hi sohailgagai
You've had some very good advice posted here. It's essential to know what type of diabetes you have, as the type and treatment will have some differences. As your glucose levels are seemingly high, it's so important that your doctor can prescribe you medications appropriate to the type of diabetes you have. There are many different medications that your doctor can select from so, if one doesn't suit you, then see your doctor again to explain to you why it doesn't suit you and he can then decide the next medication to try.
Metformin is a good medication, particularly useful for Type 2s who are likely to have some degree of 'insulin resistance', which is most of type 2s. Occasionally, Metformin isn't tolerated well but there is another version of this medication which has a slower release/action and tends to be better tolerated. It's generally better to take Metformin with, or straight after, food in order to minimise any effects. I take Metformin and have no side effects, as many others.
If you are type 1, you will need different treatment which will include a prescriptioin of a Glucometer and test strips, along with a prescription of insulin, given by injection.
It is important to have your glucose levels in good control to avoid the later complications which can result from long-term raised glucose levels. Please arrange to see your doctor and get advice. We can't advise medications on here so you really should visit your doctor, for your own sake. If your depression is making this difficult, it is even more important to see your doctor, explain how you are feeling, what medications you do or don't take and let him have the opportunity to help you deal with all this.
Good luck