?!?

ok, i have no idea what's going on wih my heart. i asked my doctor, but nobody seems to take me seriously. for about 5-6 months now, i've been expeirencing a dull aching in my heart, with the ocassional stabbing pain. i've learned to sort of live with it, but am now wondering if it's a serious problem. the doc says everything "sounds" fine, but if there's pain can it really be nothing?? any advice is good please.... when i was younger i did have a murmur, if that helps at all. thank you!