Pain Under Left Arm

Hi

I am just 25. I am in field of software.So sieating all time on computer.
From last couple of days ,I am feeling pain under my left arm and also some pain on top side of left chest where heart resides.

I had same pain 8 months back and I consulted Dr, they just said muscular pain.

But htese days ,eve when I sleep and keeping chest bed side, it hurs me and sometime I feel suffocation as well.

My weight also got increased by 3-4 pound in last 1 year.I dont feel anything bad during normal life or still not feeling any tiredness.

I am not doing anythign in any exercise or sports.
I jsut take 20 mins walk each 2 time in a day.

I just want to ask ,is it related to heart problem.Should I consult dr again.
From family history my mom and dad does not have nay prob related to heart.
My grandmom has problem of valve in heart

Pls let me know what experts feel