Whats wrong with me, I'm scared?

Ok so today and yesterday I went tramping/hiking. At one point where it was really hilly, I got really sweaty and it reached a point where I found it so difficult to breathe, no air was coming into my lungs, I couldnt breathe. And the sweat from my face was pouring down my face, and I kind of fell down (not really faint)and my hands started shaking. That happened like 3 times during the tramp. I don't understand what it means. I was like the second unfit person in my group (back of the line while tramping), no one was sweating or breathing as heavily as I was. I sweat alot generally, even while taking small walks. But I have never fallen down shaking. I'm not overweight or skinny. But I dont understand why I breathe so heavily, and SWEAT ALOT. someone gave me sugary drink, and I felt better. Recently I havebeen getting tired so easily, my parents always say I'm really weak, and now I believe that too, its getting scary. what do you think is up with me?