resting HR @ 130

For a few years now i have been tested for high pulse rate.. the lowest my resting HR was 115.  The specialists have never come up with anything.  A few months back i went to hospital for chest pains, my HR was 120 on average.  They said it was stress. send me home with anti depressants and sedatives.  I took these for a short period of time and realized i didn't need them.  Most recently;  I went to hospital last night because i have a chest cold.  My resting HR is 131 and when put in anxienty moments or when just standing up it shot straight to 142 average.  They wanted me to stay the night but i refused as i am in another province from my home town on vacation.  Any suggestions as to why my heart rate would be up so high on a regular basis... and why the medical professionals just "give up" and say nothing is wrong?