All three of my pregnancies were accidents. (i.e. I never felt like I prepared adequately for them, either healthwise or weight wise, I too struggled with some guilt of thinking "I could have been a better mother if I had started from a healthier position! But when you got what you got because you didn't plan ahead, work with what you got and do the best you can from here on out! Which is what it looks like you're doing
So good job! And quit feeling bad about it!)
I got gestational diabetes with all three of them. You can get it even if you're not obese. I was for the first two though. I didn't really REALIZE until the third one how much easier being pregnant was and controlling the diabetes was without a ton of extra weight, and I was only 20 lbs lighter for my third baby! The difference was incredible though, watching my body chemistry stay level because I was watching it through my blood sugar numbers was just so great for me. When it comes to diabetes there's direct correlation between your weight and HOW you feel and HOW much energy you have and HOW well your body handles the extra sugar in your blood. Its so much easier to control with just a little bit less weight.
For me I had very high risk factors because my dad is a diabetic (and thin as a rail if it makes you feel any better). Sometimes you're gonna get because you're gonna get it, extra weight just makes it somewhat harder to control.
That being said, my Chinese labmate who is probably 6 months pregnant and still only 75 lbs just failed the one hour test last week, but passed the three hour test. My other labmate who was probably 100 lbs heavier than me passed the first test with no problem when she was pregnant. I failed both tests and I'm pretty much destined to get diabetes with the full blown disease at some undetermined point in the future.
One thing that I did appreciate about the pregnancy though, is that it was easier for me to eat healthy when I knew I could be damaging my baby. If its out of control, it CAN cause stillbirth. Also if you don't control it, your baby is going to have a higher birth weight and puts him at a higher risk for diabetes later on his life.
For me, if I think I'm just hurting myself, I'll go for the extra piece of cake
But when I knew I was potentially hurting my baby, AND I had to prick my finger an hour later and LOOK at the consequences of my blood sugar levels as a result of that extra piece of cake....it made it a LOT easier to control my diet!
SO-don't be sad either way, although I hope you all the best that you pass the three hour test! They actually the "limit" levels set pretty low for the first test because they'd rather test more people on the three hour test and find ALL the diabetics, vs letting a few slip through and not caring for a diabetic pregnant woman properly. Do you know what I mean? So there are lot of people who fail the first test who aren't diabetic. They set it up that way on purpose so they don't miss anyone who really has it.