I noticed that when i get that heavy feeling after or during exercise, it means i'm riding the line of what is good and bad to do. If I go right up to that line, I continue to progress. Heck, I progress either way but when i go over that line and make my head hurt, I find I am just emotional and weirded out for a few days but I still make progress physically.

I'm glad you are exercising. This is good progress!!! I believe this will make you feel better.