How your iron and B12? Anemia can cause most, if not all of that.
dehydration. It sounds to me like you are dehydrated. you need to drink a lot of water, not to fast, and have a sports drink. like a gatorade or power ade with electrolytes. you resting pulse is pretty high. with out enough water and hydration while working out your muscles will feel fatigued and it will feel very strained to do any normal activities.