I Was Recently At The ER Due To Chest Pain,

I was recently at the ER due to chest pain, shortness of breath, vomiting and just not feeling right. I was released hours later all test came back ok except for elevated liver enzymes. No I dont drink and havent in over 10 years. Did a follow with my Doctor he said he wasnt to concerned. Well when I walk up the stair I am out of breathe and sometimes get dizzy. Yesterday I was having heavyness in my chest and just not feeling well I have been waking up at 2 am not able to go back to sleep. What is going on