What Causes Pain In The Upper Left Arm?

I am a 26 year old female, heart disease runs in the family on my fathers side, i have not been diagnosed with anything yet.

I have been having upper left arm pain and arm weakness for the past 3 months, but the last 2 weeks it feels as if someone is squeezing the upper arm at times. I have also been having chest pains, on my left side breast area and middle, along with back pain same area, and it does twinge a bit when i breathe. I went to the doctor yesterday and he is looking into it, did a cholesterol test but won't get test back til monday now probably. He listened to my heart and it sounded fine. I do have an acid reflux problem.

Now my question is, last night around 5 o'clock i had sharp pain in my left upper arm and felt a bit dizzy for a few minutes but the feeling went away, and also had some chest pain/discomfort. I kinda wanted to go to the ER to just be sure it was nothing serious but my mom persuaded me not too cause i was just at the doc's. I'm feeling okay this morning but still have the left arm discomfort and am just worrying that maybe it was a minor heartattack, am I being crazy or should i go to the ER for an EKG?