newly diagnosed, need insight on treatment

hi everyone, i'm new here, just diagnosed with breast cancer in november & i've just turned 37. i'm struggling with what type of treatment i should do, given my circumstance, and am looking for some insight from others who may have gone through this themselves. 

 i had a lumpectomy with sentinel node biopsy.  my tumor was a strange one, it had a cyst that was growing from it at a very fast rate.  the tumor itself scored a 9 out of 9 on the scale for aggressiveness and is estrogen postive, hert2 neg.  the tumor size was 2.4cm, with clear margins, with the exception of 1 side where there was only 1mm of clear margins.  the surgeon is going back in to take a bit more tissue from that spot so she feels more comfortable.  she also took out 4 sentinel lymph nodes, and 1 auxiliary for good measure - they all showed clear of with the exception of 1sentinal node that showed a few individual cancer cells dotted throughout when they did some sort of microscopic dye test - but they are calling it "no lymph node involvement".

my question is this - i'm really struggling with the idea of chemo.  i have a lot of concerns about what it does to your body, your overall health both short & long term, and i view it as a last resort sort of measure.  all of my doctors however, are giving me the hard push to do it.  my first inclination, since i technically have "clean margins" and no detectable lymph node involvement, is to do tamoxifen for 5 years with the radiation therapy.  but the oncologist keeps telling me things like this will mean that i could die in 5 years and that without chemo i have a 25 to 50% chance of it coming back either in the breast or somewhere else in my body...and then i get all emotional and i can't think rationally in the moment and i start to feel like if i don't do chemo, that i'm going to die in 10 years.  

 is there anyone who has dealt with the same sort of situation as me?  has radiation & tam worked for people?  how do i go about getting a second opinion from a different doctor?  should i go to an entirely different hospital to get that 2nd opinion or just another doctor in my current hospital?  i've read many things that say with my sort of cancer, the standard treatment is radiation & tam, but then the oncologist says because it's aggressive that i should do chemo or i'm taking a huge risk with my life. i'm confused and overwhelmed.  i obviously don't want to die, not now or 5 years from now, but neither do i want to pump my body full of unnecessary poison as a "preventative" measure.