I want to get a Master Degree in Occupational Therapy, but there is no Bachelor degree for OT so what bachelor?

You can actually get a Bachelor's degree in OT (see example: http://www.ithaca.edu/hshp/depts/ot/programs/ot/). Another option is to get a BS in a related field (e.g., speech language pathology), and then to continue on to get your master's degree in OT. If you get a BS in a different field, the master's program is likely to take an extra year to complete (e.g., typically, w/ a BS in OT, it is a two year grad program, but it would take three years to complete w/ a BS in an unrelated field).