Heart problems? think im dying?

there is alot to explain so i will try to keep this as simple as i can, about 3 months ago my mom gave me some target brand medication for the flu. the night she gave it to me i reacted very bad too it, it was one of the scarriest nights of my life. i felt like my heart was stopping and when it felt like that i took a deep breath and my heart would race, this happened many times that night, sinse then ive seen my docter and he said m heart was fine. but i still suffer from many things that i cant explain why they are happening. some of the things ive experienced is weird breathing, sometimes it feels like im not getting enough air. my nose always feels stuffy even though it is not. another thing is wen i breath it feels like my throat is opening and closing as if something is in the way. as for my eart it is off and on at random times. i notice it alot when im resting. usually right before i go to sleep or when im sittting on the couch or in a car ride, or during a movie, it feels like my body slightly goes numb and i cant feel my heart beat anymore, thats when i start breathing heavilier and i noptice my weird breathing. other symoltoms ive gtten are headaches in the mornings. sometimes right after eating ill get a really hard pain in my chest for a few minutes, ive told my mom about this and she says it could be from either caffeine or low blood sugar but ive been modering both and i still get weird symptoms, sometimes i feel really tired and wanna just give up on everything, even breathing, sometimes i feel like not dong anything at random times, its so weird andd then my body goes numbish right after. i am really scarred about this, please any imput will help, and no i have never done drugs or drank alchahol, a few years back before all this i drank energy drinks but never enough to do anything to me i think.. anyways im really scarred please help