Constantly tired, losing weight, no motivation, could this be hyperthyroidism?

[AHamsterPig]

So for about the past 2 years I've noticed me getting steadily more fatigued each day. I eat more than most people and I put on no weight,  in fact these past 8 months or so I've lost about 30 pounds. I was already skinny before at only 150 lbs and 6 feet tall but now I feel.. I don't know how to really explain it. I just feel weak. It's hard to stand up straight, my back is always hurting, I just have no motivation at all anymore. I just want to stay home and be lazy all the time. I've had asthma since I was little but now that I'm almost 20 years old I've almost grown out of it and I only start wheezing every now and then. I've also heard hyperthyroidism can cause shortness of breath and I'm not sure if it could be that or just the asthma now. It might not be a symptom but my hands and feet are always cold too, sometimes my whole body will be cold and then without the room changing temperature I'll start feeling much hotter.

Now just earlier today I was over at my friend's house and I was standing around with them when all of a sudden I started getting very lightheaded, my vision started getting very blurry and blacking out. I felt a really intense pressure in my head, my ears started ringing and I started getting very hot and sweating. Now I'm used to getting head rushes often from standing up quickly, but I was already standing and this felt very different. It wouldn't go away for about 10 minutes and I could hardly see. When it first started coming on I starting grabbing some water and I could hardly make out the outline of the cups in the cabinet. I sipped on the water and it finally slowly subsided. If anyone has any ideas what's going on please help. I just don't feel "normal" anymore and I'm scared that if I don't act now it could get worse.