With my first baby I started to dry up at 7 months, so I drank an herbal tea every day called Mother's Milk (I got it at GNC or Hi Health) and my milk came back full force. It also really helped my SIL who had difficulty producing enough milk to begin with. There are also stronger concentrations of herbal mixtures that aid milk production (like Fenugreek) you can take that might even be more effective. Try Baby Mother and More on the SE corner of Gilbert and Southern. They have liquid herbs you can take and can refer you to a lactation specialist. Try to eliminate stress from your life, as that can hinder milk production. And if you worry about this too much, it will only make it worse. But I was very stressed when I started drying up because I also wanted to nurse for a year, so it's easier said than done.
This time around with my new baby, I asked my doctor upfront what I can do to prevent drying up and she said her biggest advice was LOTS of WATER WATER WATER and PROTEIN in my diet. So I eat a whey protein shake every day (bought the powder at Costco) nuts, peanut butter, beans, fish, tofu, and meat. I don't like meat much, so my diet was very deficient with my first baby, but now that I'm aware, I'm very careful and eat high-protein and high-caloric foods since I went underweight last time. I think that's why my body started drying up last time. I've also heard brewer's yeast can help. And one more thing--make sure you are nursing at least 4-6 times a day.
Good luck! I was able to produce milk and nurse my first child until he was 1 year old after thinking it might be over at 7 months. I hope you have success as well.