Hello, I Have Been Lifting For About Ten Years I

hello, I have been lifting for about ten years i am 25 210 6'2" my bf% is around 10 using calipers. Every time after I lift I become very dizzy and extremely tired. I have tried different amounts of carbs both long chain and short chain and both together before lifting, I drink a lot of water usually around 48 ounces total before during and after lifting. I take a multi vitamin and creatine as supplements. I have tried increasing my iron intake in case I was low and wasnt receiving enough oxygen, i have tried more and less electrolytes, I have tried stopping creatine and no matter what I do I am always tired and very dizzy. I went to the doctor to have my blood tested and I was a little low on blood sugar but i had not eaten in a while which is rare in my case, also my blood oxygen was a little low. I have a very slight case of asthma that I use a inhaler to control. I am in good shape cardio wise as my job is unloading trucks and my heart rate is elevated for extended periods of time during the day, and I run after my workouts sometimes. what is wrong with me and what do i do??