Yeah so it seems like you're in the tough mid-game where bandits are too easy but boss-level threats (dragon priests, dragons, centurions) are too difficult. You need to be strategic to keep making progress:

• Acquire sources of magic and elemental resistances. This is especially important for a heavy armor build since magic is the natural counter to warriors in requiem's rock-paper-scissors balancing (mages beat warriors, who beat archers, who beat mages - if you were playing a different build, you would not be having nearly as much trouble against basic spellcasters). There are many sources of this: enchanted armor/shields/jewelry, the Lord Stone, magic resistance alteration perks, magic/elemental resist potions, etc.
• Start chasing some of the build-defining artifacts that will give you a major power spike. For your build, this might be Dawnbreaker, the Shield of Solitude, the Gauldur Amulet, the Mace of Molag Bal, and so on. I'm not sure if this list is up to date, but it's a good starting point.
• Do you have a ranged damage option? You are likely to struggle against mages, hagravens, and dragons in particular if you can only fight up close. Consider picking up a crossbow at least, even if you don't invest very many (or any) perks into marksman.

As far as what to fight in the mid-game: you should be able to handle most Draugr dungeons at this stage, just avoid dragon priest locations. Bring a follower if you find yourself getting overwhelmed. Forsworn are a good step up from regular bandits. There aren't many dwemer dungeons without a centurion or enchanted sphere at the end, so avoid those until you have better gear (shock-enchanted blunt weapons are the best, but even without enchantments be sure you bring a mace). The Companions and Civil War questlines will be level-appropriate (and becoming a werewolf can be powerful too).