I have an adult child that is living with me. My husband and I are living seperately for the past year, I had income, he did not. How do i file?

I believe my husband is drawing social security disability although he won't disclose this information. He doesnt' want me to file married filing jointly. I assume he is concerned my income will interfere with his SSI. My unemployed child that lives with me has had no employment the past year and is 20 years old.