While I'm in the UK, so I can't speak for Belgium, I should imagine that if you were to go to the police (a department that your ex doesn't work in), they would take your claims seriously if you show them any wounds you have..
While going through the motions of proving you're of stable enough mind to not be self harming said evidence, this won't be pleasant or a thing you want to go through, but the alternative is as the others have mentioned, possible and likely complications with any sudden attempts, or further abuse should you do nothing..
I am sorry that you are in this situation, and have to face this, however I implore you to reconsider and think things through. By all means, your choice is your choice when it comes to you life, however this seems like too sudden of a thing to rush through.. All the best and good luck.