Can I be removed as a trespasser if I have been living for 4 months in a home rented by a tenant and I have contributed to rent?

If you do not have a lease, your arguments are going to be weak. With that said, an argument can be made that since you paid the rent you are not a trespasser but instead a tenancy was created. The default would be month to month which would entitle you to a notice at a rental period term or one month most likely under these circumstances If they remove you as a trespasser and you have paid rent you have a right to seek reimbursement of those funds.