Do I have heart problems?

I'm 17 and for about a year now I've been having palpitations and an irregular heart beat, but very recently they've got worse. It only used to be very mild and happen every so often but now it's pretty much constant and is causing pains in my chest, throat and jaw - the other day I actually ped out because of it. I've been under lots of stress recently, and I know that can have effects on you but it's never been this bad before. I'm worried it could be serious - my family insists it's hereditary and I shouldn't be worried, but I'm still concerned. Anyone out there with medical knowledge who can help me?