55% is a perfectly respectable mark.
Frankly you sound rather closed minded about the discipline you're studying. It doesn't sound as though you've got the hang of independent study.
For example, do you regularly go beyond the reading list and the lecture sources in your essay research? Because you should be doing so -- particularly half-way through your degree.
When you read the secondary sources that you use to help you prepare and write your essays, do you think about how those writers are writing? That would help you develop a greater sense of depth in your own writing. We often set readings as much for the examples they set in how to write history, as well as for the information they contain.
You also sound quite dependent and lacking in initiative in terms of seeking help. You can dismiss your personal tutor like that, but there are many members of staff in your Department, including the lecturers & tutors in the modules you're studying. Have you ever taken your essay, with feedback, to an office hour of your lecturer or tutor? Do you go through marginal comments and the narrative feedback (NOT the mark) with each essay? Do you make an appointment (generally by email) to see a tutor to discuss this feedback?
These are all standard things you can do within your subject. And creamteas has suggested taking the initiative to get some generic help about essay writing -- it's ALL there for the asking.
If this list of things you could do makes your heart sink, then maybe you're not ready for university yet. There's no reason why you should be. It might be better to do something that really excites yo. You can always go back to university later in life, or study Distance Learning via the Open University. There are lots of ways of learning. It's really not compulsory to go to university & perfectly possible to succeed in life without a degree.