Forced heart beat feel? WHAT COULD BE WRONG??? only 16 and heart problems already!?

ok i know this is long but please read and give me your thoughts or info! I am going back to the cardio doctor so im not trying to diagnose myself but to just have some ideas. Ok so its been about a year now I will be doing apsalutly nothing and or I could be doing very heavy excersize and it can vary but i will have a shark pain like Im being stabbed in the heart and sometimes it lasts only a few seconds or a couple of minutes. it happend severly while at swim practice so i got out and i couldnt breath so they put me on oxygen and called paremedics. by the time they got there 30 min later i was fine so there was nothing to see or hear. i then went to the heart doctor and they found that i have an anurism in my heart on the aorta and the anurism has a hole in it. they said i would be fine but to watch it when i get to my 20's to 30s, they talked about fixing it or blood thinners but said i was young enough i should be ok. but if a clot or partical were to get through the hole it would go to my brain and kill me. anyways it got better but its been happening again and it feels like i cant breath and what is really bothering me is it feels like my heart is being forced to beat, that its taking all my energy to keep it beating. I am only 16 but with the other heart problems i dont know if its somthing to worry about and what could it posibly be?! thank you so much!