I don't know if you will relate to this or not but I had something similar happen to me. Back on Christmas day of 1982, I came down with a really bad stomach bug after which I was never the same. Prior to coming down with the stomach bug, I was a junk food junkie and was addicted to anything with sugar in it. After the stomach bug, I had symptoms that in hindsight were like a milder case of ME/CFS then what I have now. I went to the doctor with no relief and in desperation decided to give up all junk food and anything containing sugar. I started eating nothing but healthy food and to my surprise ended up feeling much worse. I went back to the doctor and told him what I had done and how much worse I was feeling and he decided to run a glucose tolerance test on me.
I went and took a 4 hour glucose tolerance test and at about 1-1/2 hours into the test I started feeling so sick that I wanted to leave. I felt like I was coming down with a bad flu bug. The lab technician convinced me to stay and finish the test. But, the fact that I had felt so sick in the middle of the test piqued the lab tech's curiosity so he immediately started running my blood through to get the results. He then told me that he wasn't supposed to tell me the results but he felt sorry for me and decided to tell me that I had the worse case of reactive hypoglycemia that he had ever seen which my doctor later confirmed.
I was then sent to a dietician for a diet plan. I explained to the dietician how I had felt so much worse when I switched from a junk food diet to a healthy diet and asked her if she could explain why that would happen. She said it was because the junk food was loaded with fat and although it had more carbs and sugar than the healthy diet, the high fat content was buffering the effects of the low blood sugar and providing my body with an alternative source of fuel. She said when I switched to the healthy food diet, I was eating very little fat and more carbs than my body could tolerate. So, when my blood sugar dropped there was no fat in my system to buffer the effects of the low blood sugar.
I don't know what kind of junk food you were eating but if it was high in fat and then you switched to a low fat healthy food diet is it possible that you are experiencing low blood sugar attacks?