well...it's master difficulty....what do you expect from it??try build a new char using shield+one-handed and invest your points on:
1. one-handed
2. block (quick reflex if you want to dodge or bash easily)
3. heavy armor
4. alteration (mag res perks)
5. alchemy
6. enchantment
and take a Lord Stone effect and Agent of Mara for phy dam and mag res (with a breton you can have 85% mag res, and mages will be nothing at all)
this build in general is the most easiest to play on master difficulty..right now i'm doing a re-run with dual-wield
ooh and btw, you should choose your companion according to your build,in this case ur a melee and a tanker,so if i were you i would go for Illia (mage) or anyone who specialize in range (Aela maybe)
don't be discourage by it,if anyone can do it on master,so can you..you just need to try a bit harder and play with more careful and use your surroundings to take the advantage...
right now i'm using extra mod for difficulty, PISE, it improved AI and mobs spawn are 50% more...
my advice,keep using skills that would benefit for you in the near future...at level 4 when i fight Milmunir,even with a shield raised she bite me and my health went down almost empty,but before i reach level 10 i can take out standard dragon without getting hurt at all..and when you get the Elemental Protection on Block perks (50) you can raise shield against dragons breath and watch you're health going down very...very slow...and trust me before you hit 20,you'll feel unsatisfied by the master scaling and want more challenge..LOL
cheers bro and good luck