As far as I know, there's nothing special about being postpartum that can lead to diabetes, but diabetes can occur at any time of life, including during or immediately after pregnancy. If you're concerned, I'd probably get checked, as it's better to find out and get treatment (even if the treatment is just a different diet and more exercise) earlier rather than later.
There are a few different diagnostic benchmarks that are used to diagnose diabetes these days. One, as a pp mentioned, is the GTT, which is pretty much exactly the same thing that you do during pregnancy. You go in the morning, they take a fasting blood draw, you drink the glucola drink, and then they do blood draws at 1, 2, and 3 hours post-glucola. I'm not sure how many of your numbers have to be out of range for an official diagnosis using this method. I do know that if your fasting number is greater than 126, that's enough for a diagnosis right there. They can also look at your hbA1C level, which is a sort of average of how your blood sugar has been running over the past 3 months, weighted more heavily to the last few weeks. And, finally, any test that is over 200, whether fasting or not, is indicative of diabetes, although I think the diagnostic standard for that is that you need two separate instances of >200 before diagnosing. Then there is a kind of a middle ground where your numbers are higher than normal, but not high enough for an official diagnosis of diabetes, and that's when you'll be called "pre-diabetic" -- basically, your body isn't processing glucose correctly, but it's still processing it enough to avoid causing serious damage to your body for the time being.
Wow, I did not mean to go on for so long about diabetes diagnostic tests.
Anyway, I agree with the pp who said that a lower-carb, higher-protein/higher-fiber diet is probably appropriate at this point. I would personally probably make an appointment to get checked at a doctor's office just in case, too. Especially if you are having symptoms, such as fatigue/exhaustion/sleepiness after meals, excessive thirstiness (although I know that's a breastfeeding symptom also
), unexplained weight loss, blurry vision, or tingling/numbness in your fingers and toes.
Good luck! I hope it all works out for you!