Ffs Ive tried like 7 times to beat one but damn his fire breath damage is huge , my dragonborn is lvl 40 sword and board char, equipped with Ysgramors shield and the Pale Blade and ebony armor.

Im so mad and dissapointed of myself now

Get some magic resist gear or take the shield perk for 50% magic reduction.

Do peryites quest, get the dwemer shield spellbreaker, try again. I had the same issue you did till I did that haha

What difficulty are you on? Dragons shouldn't be that hard if you know how their AI works. Do you know the Lesser Ward spell?