PookaMustard: Are you playing with a controller? Typically such games encourage you to use a controller instead of the keyboard.
If you wish to beat the game, one of the things you should do is analyze the bosses. All the bosses have patterns. The other is not to rush through the stages, and carefully move through the stage.
Yeah, I'm using a wireless Xbox 360 gamepad. Maybe it's the input lag. I don't know. I have no problem using the gamepad to play GTA V or the keyboard and mouse to play Half-Life 2 on hard difficulty. I'm okay with a game being difficult, but this is noticeably more difficult than Dark Souls, and if you play it on the easiest difficulty, it won't let you progress. That's just flat-out unacceptable, and I'm far from the only person who's had this issue. Polygon described it as "...a comically difficult, if not cruel, experience...".