What Causes Dizziness, Tiredness And Pressure In Upper Left Chest?

Yesterday I got really dizzy to the point I felt like fainting I also was experiencing bad tight like pressure in my upper left chest and got extremely tired fell asleep and still heard what was going on around me but couldn t wake. This was not the first time this has happened to me and every time it happens I just want to sleep for the next several days. What can be causing this?