You mentioned that you have a baby that is 6 months old, and you also have diabetes, but it sounds like it's well-managed because you have an A1C that is 5.6. And you've been breastfeeding, you've been taking oral contraceptives, and in spite of all of this, you are pregnant. And you said that you're a little bit scared to tell your doctor because they told you to wait longer, and you're wondering what implications this might have, and "What should you do? How did this happen?" So I always say that all babies are miracles, but some are extra miracles. Really, sometimes there is no other explanation other than "this baby was meant to be". I've literally had patients that the woman had a tubal and the dad had a vasectomy and still had a baby somehow.
There is no contraception out there that's 100%. When it comes to oral contraceptives, the failure rate is 0.1% when taken properly. But because most women miss pills here and there, or don't take them at the exact same time everyday, the failure rate can be as high as 8%. And breastfeeding is not a sure form of contraception. Technically speaking, it does affect your hormones to the point where it suppresses ovulation, but if you've had a period since you've had your baby, your baby is older than 6 months, you've been supplementing with formula, or introduced solids, then the chances of you ovulating in spite of breastfeeding are great, and pregnancy is a possibility. The combination of these 2 failure rates might be why you're pregnant, but I do recommend that you call your doctor as soon as possible, and make your first prenatal appointment. And know that there's no reason to be ashamed.
Your doctor can talk to you about what the risks are (because it's only been 6 months since your last C-section), establish a sure due date (because if you weren't having regular cycles, you may not know how far along you are), and also discuss your diabetes, and it's very important that you continue to manage that. And because of your history, you are high-risk, and that makes it even more important that you seek prompt prenatal care. As you found out with your last pregnancy, you'll be watched closely by a specialist to make sure that your blood sugars are well-managed. They'll watch you and your baby, and hopefully that will help to prevent complications from happening. When it comes time for delivery, your doctor will talk to you about what the most appropriate delivery option will be - a vaginal birth or a C-section - depending on your history. They'll also talk to you about the risk of uterine rupture, because after you've had a C-section in the past, you're chances are slightly higher if not much time has passed since you had your last C-section. Your body does of course need time to heal. If you have any other questions for me in the future, feel free to ask them on our Facebook page at http://www.facebook.com/IntermountainMoms, and recommend us to your friends and family too.