I don't have diabetes, but all my siblings are Type 2, so I keep up with information to avoid it for myself. Do NOT add carbs.
It's possible that your IF is causing the increased BG. What I've learned is that ANY food eaten in large quantities will elevate blood glucose, so that if you want to control your blood sugar, you're better off eating smaller meals more frequently.
My sister, a Type 2, has a really busy job and she finds that often she doesn't eat all day and gets most of her calories in the evening. Even though she's not eating more (total food for the day) than she would if she had 3 meals, her BG goes over 140 (when it normally stays below 100) with that big meal.
Dr. Richard Bernstein warns against this ideal of larger meals. He points out that even protein (meat or fish) will elevate BG if the portion is too big.
If I were you, rather than continuing to monitor your BG, I'd ask the doctor for an A1C test, which gives your BG average over three months and is accurate in identifying any real problem.