this is very like the way it happened for me. I did lose weight after baby 2, (she was 9-2, and I went to 173, but back to 140, which was still much more than after baby 1) and my fastings and a1c slowly went up, but still within normal. I was about 48, and up to 170 ( had been slowly gaining, and not LOSING) when I started to have excess thirst and peeing. Did the 3 hr test, (fasting, 1 hr, 2 hr and 3 hr sugars) and the 1 hour very high, 2 hr normal, 3 hour abnormally low, fasting normal too.
SO that was the official start of pre-diabetes. I am still officially there. I take metformin twice daily, and still struggle with weight issues and overeating. I really crave carbs, and recently started to treat that issue as an addiction, so far with some success.
I am proud of you if you can bring the weight down before you get here. Remember though, that is it NOT you fault. There is good research to show that those with a diabetic predisposition, especially genetic, may have problems losing weight.
Also, this pattern you are seeing is very common (read on the website blood sugar 101) and see about ways you can help yourself and stay as healthy as possible.
zen and the art of weight loss, finding the true path of en-lighten-ment