The shots are too hard to see, the enemies aren't very interesting, and level design doesn't give the impression of having been designed. The enemies just float by shooting in no particular pattern, and there's no sense of how to avoid getting trapped by shots, especially when more enemies show up. Were you able to beat this without getting hit? If not, did you test for the ability to beat this without getting hit? If neither, then it's a safe assumption that your game is unfair.
Also, on a technical note, unpausing doesn't clear input, so if the game is paused while the player is pressing "a" or "d" (such as due to accidentally clicking), then that direction is still considered as being pressed when the game resumes.