Spring 2019, I was diagnosed with type 2 diabetes with an A1C of 7.2 and fasting glucose of 108. At the time, I was 285 lbs (5'8") and drinking 5-6 can cokes a day. For years, I dealt with my depression by seeking that instant gratification from drinks and sweets.
That blookwork was a wake up call. I immediately cut out all sugary drinks, kicked the sweets, and started actually paying attention to what I put in my body. Same as you, I had a bad headache for a couple of days and then was over it. I lost close to 20 lbs in those first couple months afterward.
I'm now 210 lbs and slowly but surely still losing weight. Without medication, just diet controlled, I've gotten my A1C steady at 5.0-5.5 for the past 2 years. That's still eating 30-40% carbs, just making healthier choices with no refined or added sugars, whole wheat and grain when possible, and plenty of fiber.