What Causes Excessive Hair Loss?

I have a lap band that slipped about 5 years ago. Since then I have had a bad diet due to only being able to eat things that either crumble (cheetos), liquids, or things that melt (chocolate, sour cream dips, or cheese). If I try to eat vegetables, fruit, or meat I ll throw up right away. The question, could this bad diet cause my hair to fall out. It has been coming out lately in clumps. I had pneumonia with surgery (2 liters of puss in my chest an lungs) in March but I m fine with that. The only problem that I ve had before and since the pneumonia is my lack of energy. I had pneumonia for a week & half before I went to the hospital. I was just so tired I thought it was something else. Could this poor diet have anything to do with my hair coming out. Thank you, Doug Gaskins