Pain in left chest. This. pl advice me.

I am 5ft 10 '' tall weighing 75 kgs and my lipid profiles is normal.I walk briskly for 45 mts.covering a distance of 5 kms.in the morning.I don't have any cardiac problem except for when I talk loudly or loudly and continuously over phone.Then I develop chest pain and this pain percolate down the left arm and I feel uneasy.This problem is there for long.Some 6-7 yrs.back I showed it to a cardiologist and on doing all the tests and tread mill for half an hour at high speed,doctor said no problem and if you want more than I have to do other check ups.This problem arises very rare when I talk for long hours with voice louder or when I get tense.During physical activity I don't develop this.Pl advice me.