Hi NiceGirl,
If you are feeling weak, I doubt you're getting enough nutrients. Like everyone else said, get something to reduce the stomach acid. If one doesn't work, ask for a different one. There are lots of Protein powders and ready mixed drinks out there that do not contain lactose and their are also milks that are lactose free. So, fortunately, in 2010, they are making a lot of lactose intolerant products.
Walking everyday will improve your mood and energy levels and carry a Water bottle with you when you go and listen to some good motivating music. Some exercise will also preserve your muscle mass. The body will lose muscle mass before fat if we don't get in enough protein.
B-12 and/or B Complex - There are sublingual tablets and I personally like the gummies (red raspberry flaver from CVS...taste like gummy bears...small, easy to chew, and you can take more than one if you an energy boost). I've also seen sublingual liquids in a dropper that you hold under your tongue for 30 seconds and swallow. Wal Mart, CVS and GNC carries the liquid.
Are you becoming dehydrated? make sure you get in enough liquids and protein to keep up your energy. If you are feeling this bad at a month out, you might want to schedule some blood work to see if something else isn't going on and to make sure your nutrient levels are adequate.
Don't compare your weight loss to others. I'm sure you already know this and it's hard to do. I choose not to weigh myself daily. I don't keep a scale in my house. That way, I don't focus on pounds.
How's your blood pressure, cholesterol or diabetes? Were you on any meds? Have you been able to come off of any? (other than acid reducers)
Hang in there; you are losing more than the recommended 2-3 lbs a week.