Hi trekpole, try not to worry too much about the weight gain. If you are anything like me than your weight can fluctuate by this amount on a daily basis. Concentrate instead on taking care of yourself. You've made some terrific steps by cutting out the sugary stuff, and the exercise will be doing you the world of good, even though you may not be aware of it yet.
I can't remember - do you test your blood sugar levels? If so, then when you are feeling weak and faint as you describe, you should do a test to see if it is due to your levels at that time, or if you might need to look at other possibilities - not everything can be attributed to the diabetes, and I think we tend to forget that sometimes as diabetes is so foremost in our minds.
What Wallycorker says is very true - diabetes is a condition that you have to learn to manage mostly by yourself, using your own experiences and those of others (by asking questions here, for example). Doctors quickly reach a point where their generalised knowledge is insufficient to apply to your own specific needs. They are good for prescribing stuff and doing tests etc., but even the great ones sometimes struggle to help, not being so intimately involved in the situation on a day-by-day basis.
Build up a diary of knowledge you can refer back to - record your food and exercise, how you felt afterwards, and your levels if you are testing (which I would highly recommend whilst you are gaining knowledge about foods and how they affect you). 🙂