I HATE my Brain....sometimes

I hate my brain sometimes.  Since my last journal entry I have went to the doctor to complain of my exhaustion and she ordered blood work which came back normal which is good.  I also have been having palpitations and feeling like I am having trouble breathing, but I don't know if this is anxiety or something I should be worried about.  I am not as tired as I was but I am scared it is just around the corner.
Also I have been having this weird sensation where it feels like a weird pressure on my left breast.  Like someone is pressing down on it.  It only last for a couple of seconds and then goes away but it has been happening the last couple of days.  My brain automatically thinks breast cancer since my Grandmother died from it and my cousin who is a year young then me was diagnosised a couple of years ago.  She is better now but she had to go with cemo and radiation. 
But it has only been a couple of days and I am already jumping off the bridge of feeling like I could be dying.  I hate that.  I hate that it takes so little for my confidence to be undermined.  What is real and what is all in my head?  I hate feeling like this.  :(