Make yourself an appt with a counselor at UCSD to get better info that the counselor at your CC is able to give. For starters there is this
It isn’t clear when you say “I can only use a few of the classes towards graduation” if you mean they aren’t relevant to your current major, or if UC won’t give you credit for them at all. If the latter, perhaps an escape clause in the snippet above.
One other thing you need to discuss with a qualified counselor is excess units. The UCs are changing their policies, but there are caps of some sort on how many units you can have if you have attending 4-year and 2-year colleges. There didn’t use to be a cap if they were all from a CC, not sure if that is still true.