CC=>UC is a path that works for tens of thousands of students each year. Given the work ethic and smarts demonstrated by your UCSD admission, you’ll find your way through, no doubt.
As noted above, transfer admission at all UCs and some CSUs is very competitive. To earn your way back into UCSD, you’ll need a 3.7 (give or take) GPA when you apply as a transfer. That’s a pretty tall order but, for someone who earned a 4+ HS GPA, it is probably doable - though since you apply after just 2 semesters, a C in one class can ruin your chances. Scheduling at many CCs can also be a challenge - you’d be making this decision very late so, i’d bet many of the classes you’d want/need at your CC are full.
The other thing is the whole freshman/dorm experience - for most, it changes the way they look at the world. Another consideration - who is sitting next to you in class. Attending a CC will be a significantly different experience than heading to top school like UCSD.
This is why I am such a big fan of transparency with my kids… this is a conversation that should have happened a long time ago but, talk to your parents and see how much of a hardship the $30k/yr will be. Since you got no aid, your family must have a solid income and asset base. If they tell you they have it covered, off to San Diego you go, no worries. If they confess it will break their bank and cost your siblings an education, it is time for plan B.
Good luck