It depends on your relationship with the company that pays you. If you are an employee, then they should be taking FICA (social security and Medicare) taxes out and paying them. You can go to the SSA.gov website and either log in or create an account to see if the benefits are being applied. If they are not, then you would need to contact them to have them update your wages for the years you were an employee getting IHSS payments.
If you get a 1099, then it has no affect on your social security and Medicare as it is not subject to these taxes.
Whether the payments are subject to social security and Medicare taxes depends on whether you are an employee of the agency, an employee of the individual care recipient, or an independent contractor. If the agency is your employer, the payments are subject to social security and Medicare taxes. See Q&A 18 under Agency Questions. If the care recipient is your employer and these payments are wages for that employment, the payments are subject to social security and Medicare taxes unless one of the exceptions for domestic services applies. See Q&A 19 under Agency Questions. If you are an independent contractor, the payments are not subject to social security and Medicare taxes. See Q&As 13 and 14.