Heart Disease and Heart Attack Forum - Heart, Stomach Or Anxiety? Would Love Any Advice

Hi, well first of all to let you know I'm a 21 year old female, never smoked, hardly drink, in the normal weight range a bit towards the skinny side, no family history of anything, no illnesses, never been really sick, only medication is the pill (birth control).
I have chest pains quite often, sometimes a few times a week. Basically it feels like my heart is uncomfortable, like it feels like something is touching it that I need to move, or it's stuck or something. It's not severe but it's very unnerving and stops me instantly from whatever I'm doing. Sometimes I also get a sore left arm. I never have any shortness of breath and it doesn't get worse with exercise, it's really random. And it's not like that stitch pain you sometimes get when you breathe in, I get that too but this is different. I went to my doctor a few months ago and he said girls my age don't get heart problems, but did an electrocardiogram just in case. It didn't show anything major except he said something about my heart taking a short-cut or something which I've never understood but he said it shouldn't be causing me any pain and then decided I had anxiety. That is possible but the only thing is I don't feel anxious until the pain starts. Sometimes it will hurt and I'll tell myself it's nothing, go to sleep and then wake up a few hours later like I did tonight feeling weird and I guess I sort have a panic attack. I think I'm dying and almost pass out I get so scared. My heart rate goes quite high when I exercise but I recover quickly and I don't puff. Is 180 b/m when excercising too high for someone my age? The doctor did give me a referral to a cardiologist for my fast heart rate but once assured I wasn't dying I didn't want to make anymore fuss about it so I didn't go. Plus he told me that my resting heart rate though high was within the normal range and it was more just for my peace of mind. That was months ago now but I still get the symptoms.
I also have an uncomfortable stomach a lot of the time. Anything really sweet or fatty makes me feel very nauseas where it never used to. My stomach never used to bother me at all but now it's almost always feeling uncomfortable. I'm not sure if these are related, if I just have anxiety or what but I just don't understand why if it was just me being a hypochondriac it doesn't disappear when I forget about it but instead wakes me up randomly. Sometimes it comes and I just ignore it for a while and it will eventually go away but sometimes it just won't go for hours until finally it's waking me up.
Also I've had a few broad blood tests including one for thyroid function, liver and kidneys, white blood cell count etc and everything has come back fine.
If anyone has any suggestions about what could be causing this or knows maybe something I can do to make it stop I would love to know.