What Could Cause Cheat Pain,lightheadedness And Sharp Pain On Left Shoulder?

Hi. For the past few years, not sure how many anymore but i know it is at least four, i have been having a lot of weird symptoms. I dont really know where to start but here goes. The first and most prevalent symptom is the exhaustion. It is constant and i have a really hard time even standing for more than ten minutes. Some days. I have a really hard time concentrating and it often gets so bad i mix up a lot of words or have a hard time recalling even the simplest of things. Another constant thing is the chest pains and lightheadedness the lightheadedness usually only occurs when i stand up and i start blacking out and usually have to hold on to something to prevent myself from falling and the chest pains aren t too severe, its mostly a pressure or heaviness that sometimes may spread to my shoulder and i get a sharp pain below my left shoulder blade when taking a deep breath. Had an EKG and kept coming up for pericarditis but then i had a 24-hour holter monitor and it came up normal. I am a 22 year old male if that helps and i really need at least an idea of whats going on because i need to start working and providing for myself but i cant because these symptoms are having a huge impact on my daily life. Any ideas would help me out even if its just guidance in what i should do next and i am happy to answer any questions that may be needed.