Without a marriage or registered domestic partnership, California community property laws don't apply. However, you're not without rights:
1. The house: If both names are on title, you're co-owners. The default is 50/50 unless you have a different agreement. Either party can file a partition action to force a sale or buyout.
2. Joint accounts: Funds in joint accounts are generally considered jointly owned. Withdraw your half (no more) to a separate account to protect your share.
3. Palimony / Marvin claims: California's Marvin v. Marvin (1976) allows unmarried partners to enforce express or implied agreements about property sharing. If you can show an agreement (even oral) that you'd share finances and assets, you may have equitable claims.
4. Unjust enrichment: If your domestic labor and childcare enabled your partner to earn more (career advancement while you managed the home), you may have claims for the value of those contributions.
These cases are fact-intensive. Document the financial history of your relationship as thoroughly as possible — bank statements, mortgage payments, division of labor, any texts/emails discussing financial arrangements.