Quick answer
Use a safer device or account to seek help. Private browsing does not eliminate monitoring.
Do now
Tell a technology-safety advocate what devices, accounts, vehicles, and family-sharing services are involved. Plan changes before making them. Preserve relevant evidence if safely possible and consider whether messages or appointments will appear on shared devices.
Watch for
Removing a tracker, resetting a phone, clearing history, or changing passwords can alert an abusive person. This library does not recommend blanket changes without a safety assessment.
Official sources
National Domestic Violence Hotline — Internet Safety, National Domestic Violence Hotline — Plan for Safety.