It sounds like you've managed to pick elements of a character build that don't complement each other.
And yes, Destruction magic as a killer is tough, very tough, to use due to the levelling problem.
One way to go is (relatively) all-out sneak, focus on archery, getting the triple damage perk as soon as possible, and pick people off at range. When they get in close, either go all out fast dual-knifey on them, or just use a sword and shield.
Alternatively, be more up front, use heavy armour, accept you cant get in any sneaky hits, but a bow isn't a bad thing to damage enemies with at range anyway, before doing sword 'n board and taking hits.
Conjuration I like to think of as a backup skill, for any class type. Fights always become that little bit easier when you add a temporary ally, and one of the conjuration mods allows you to conjur up Draugr. So yeah, my high level characters can call up a handy Draugr DeathLord!
Also, early on, pile almost all of your perk upgrades into health. It'll never be a bad thing to have plenty of, and early magic spells won't eat your Magika too much anyway. Also, conjuring a familiar is pointless. It dies in 1 hit, does almost no damage and barely raises your conjuration. Get a flame atronach spell, and if you dont have enough magic to cast it, wear a ring or necklace to grant you more, and call it for every fight. You'll soon start levelling a bit.
(Depends if you want to keep this char or start afresh)
Also, why does nobody mention the difficulty settings? I've modded my game, so I find that starting out on Expert works well for me. I'm weak, and any hulking great nord with a 2H sword who lands a hit kills me. Thats how I like it. As I level up, and become more of a badass, I'll raise it to master. Also, tho I have done it before, I don't abuse the smithing perk.
(If you keep your current character, find, beg, buy or steal an item that increases your blacksmithing, and break it to learn the enchantment. Then smith a full leather suit, necklace and ring with blacksmith enhancement. Pop a blacksmith potion, then make yourself some weapons/armour immediately after. I once had a bow which had a base damage of 236! If you get the balance right, it can help you, until you decide it's a bit OP and then ditch it)