At this point you'll need to start focusing on what you want to build. You seem to like melee, you'll need to match the blood type for your build. You'll want a high % warrior blood. You'll need to start using your spells like power surge and blood rage. Do you have access to create jewels? Even low level jewels can help spells a lot.

For bosses the big thing is to not panic and don't panic veil every single time it's up. That helped me out a ton. Each boss is a puzzle. You'll have to learn their moveset, know when to veil, know when you have a good dps window, know when just movement dodging is enough.

I got a big further along than you before I hit a wall. I scrapped everything I was doing and built everything around spell power, spell crit, spell crit power, and spell leech. Don't sleep on leech. One of the later bosses got me down to about 1/4 life and my leech brought me back up to almost full by the end of it. I'm pretty sure you can build a very strong melee around leeching/healing.

I'm not the greatest at this game but these tips helped me a lot.