Can my flatmate force me out of our shared flat?

I have been sharing a flat for three months now, paying month to month and sharing other expenses. I have emails and wire transfers to show payment, and there are emails where we discussed how long I would be staying, but there is no signed agreement. The contract with the landlord is in my flatmate's name, and I do not know if the landlord is aware that I am here.

I would think that the flatmate has to give me months notice (the term of my tenancy) rather than a week (he seems to think he is entitled to a day if he so desires). If it helps, we live in Alicante.

Thanks in advance.