Hiya liz
Yes it could be the diabetes that's making you feel exhausted. It could also be that you are coping wih something new and shocking.
It isn't likely to be Metformin, especially if you have escaped the dreaded "tummy grumblies" which it often does cause.
You should find you begin to feel better as soon as your blood glucose comes under control.
What dietary/ lifestyle advice have you been given? Metformin needs some help htere. what blood readings have you had?
Read through the forum and you will probably discover what changes you will need to make and which will suit you best. Each of us has to find our own road.
Don't be afraid to ask. someone will always come along to help.