I'm 21 and I feel really unhealthy , over the summer I had the opportunity to go on numerous trips to go backpacking and hiking, I was feeling really great because I had gained alot of muscle and had so much energy, normally i'm really small, so everything I had gained was muscle, I felt like I was at my peak, then I came back to school for a semester and I was feeling the urge to run or do some type of workout, so I did for a few weeks, and then I stopped due to my habit of being lazy, and then slowly I started noticing myself losing alot of weight and muscle, within a short amount of weeks the changes were really dramatic, I became really skinny, and I ate a lot, so now my body is weak and I feel I have no energy and on top of that I look awful, I wonder if this is normal or if anyone knows anybody with a similiar experience because i'm confused,