Problems after eating dinner

I was diagnosed Type 2 about 12 months ago, and am successfully controlled by diet. Usually 6-6.5 readings. After I ate dinner last night, grilled chicken snitzel, small portion of pasta and steamed veggies, I developed a headache , became extremely tired and my vision became slightly blurred. Symptoms came on 5 mins after eating. Thinking it was diabetic related I check my blood sugar and it was 7.5. I thought it would be much higher at that time. I felt like I needed sugar so I ate a small packet of menthos candy which helped rid the headache but still felt the need for sugar so I ate an ice cream and a small chocolate bar. Within15-20 minutes I felt normal again.
This is the second time this has happened, the first was about 6 mths ago. Dinner on that occasion was chicken stirfry with rice.
Wondering if anyone knows why this is happening?
Thank you