Hi everyone,
This is my first time posting here, nice to meet yall. I'm currently 17 this year, about 5'9" and 123 pounds. I have these 3 questions which have been bothering me for quite some time now. I was wondering if any of you could help answer them?
The first thing is the problem about my size. I am rather skinny for my height, my shoulders and arms aren't as broad as I would like them to be. I have been desperately trying to put on weight for the past few years. I do eat a lot, favourites being red meats and snacks. Yet, no matter how much I eat, I have been unable to gain weight. My stomach is the only part of my body that grows fat

I workout often and am in good shape. This leads me to wonder, why can't I gain weight? Is my the diet the cause, or is there something wrong with me(worms)? Is there any medication or supplements I can take to gain weight?
My second problem has to do with blackouts. A few years back, they happened quite frequently. I would blackout for just a few seconds. Recently, they do occur, although less frequently. Sometimes my ears will have a ringing sound for no apparent reason. I suspect it has something to do with my heart or lack of sleep. Any ideas for the cause of it?
A few years back, when I saw a GP for some other problem, he told me I had a lot of mucus. As a result, my nose was often blocked. I have to breathe through my mouth 8/10 of the time. This causes me to breathe really hard and loudly. Every morning, the mucus would flow non-stop for at least a few hours, and I would have to constantly blow my nose. This really causes a lot of problems for me. I sleep with the air conditioner every night. Is there any way I can cure this?
Any help at all would be greatly appreciated. Thanks in advance!