Health insurance in Belgium

Hello,
I got an offer for a freelancer for 9 months in Brussels, Belgium. I am a Bulgarian, so the offer includes i to be hired in Bulgaria in order to save taxes. But we are humans after all and it happens a man to get ill. That is why i would like to have some health insurance, so in case i get ill, it to cover visiting a doctor, pills, etc - all the medical treatement i will eventually need. Unfortunately i do not find any useful information. I read, that there is an option i to pay to the Belgium Health System (not sure if this is called in that way), but i will have benefits after 6 months of paying, which is not useful for me.
I will be very grateful for any useful information.