Highly recommend that you get a home testing blood glucose meter so you can see what your blood sugar is doing and also how it is responding to what you eat. You may need to change your diet to reduce your blood sugar.
It is usual to have such an initial reaction to metformin. Suggest you start off with just 1/2 or 1/4 tablet per day and then slowly increase to the recommended dose based on the resolution of your symptoms.
If this doesn't work, you can ask your dr for slow release version.
If your urine glucose is HI then you blood glucose must be way higher. if the meds don't bring your sugar down fairly quickly please ask your dr about insulin!
That is a very common reaction to Met. for some it goes away in a week or two. Also what strength met? many find starting on a low does and working up helps. The also make a Extended release Met. that many find easier to handle. good luck