how do you know if your heart hurts?!

i had some heart problems in the past. not major where i was dying, but it was pretty bad
basically i was just in so much pain i couldnt eat, move or even blink because it hurt so much. i was 16 when that happened. a lot of stress. and please dont tell me i cant go through that much stress at that age... (and no im not emo)
now im turning 18 soon and i think it's coming back
i havent been through so much stress lately, but i work out and i just got new weights and they are way heavier then the old ones and i really push myself when it comes to work outs
not to the point where i crash, but just enough to feel the muscles pumping and sometimes more

so im woundering if it's my heart that's hurting and if i should keep working out or go back to old - smaller weights
how exactly do you know your heart hurts? maybe it's something else?
what im feeling is a sharp pain in my heart area. it's liek something is stroking it with a needle
each stroke lasts for few seconds

please help!