I’d start with a gap quarter and use the time to get straight and explore your options. Once you are well into your upper division work, it is really difficult to transfer to another UC or CSU. (there are unit caps for transfers and minimum # of units you need to take at the school granting your degree) Unless it would be detrimental to your well being, it probably makes the most sense to stick where you are for the 4th year - which is really more like 8 months.