Three days in ... surprise

Sugar doesn't cause weight gain. Too many calories causes weight gain. If you're gaining weight, you're eating too many calories, simple as that.

Learning never stops. It's a blessing that sometimes hurts our pride.

Real food is harder to overeat than junk.
When starting out losing weight, we often tend to ignore feelings of hunger or other discomfort.
But there is no reason why you should be more hungry or down when you eat just what you need. Healthy weightloss is eating enough to sustain you, just little enough to let you tap into your fat reserves.
Hunger can take many forms. Lightheadedness is most likely hunger. Learning about hunger, satiety, appetite and cravings is very useful.

You have gained weight by taking in too many calories over time, not by eating any praticular foods.
What you normally ate included soda, candy, cake, pie, and added up too many calories in total.
Many of those foods are richer in starch and fat than in sugar. Calories in sugar aren't more "fattening" than calories in fat, starch, protein or alcohol.
It is good that you have a perception of a "normal" diet. That is something you can return to, and it will help you lose and maintain weight. Most people can't eat a lot of junk and stay healthy and normal weight.

I was overweight too. I changed that by eating less. I managed to continue doing that by eating better in addition to eating less. I managed that by investigating how I could eat better without feeling that I was missing out.