I'm 16 and my boyfriend is 20.

In most states the legal age of consent for purposes of sex is 16 year of age.  If you were 16 at the time that you conceived the baby, then you should be ok and there should not be any repercussions.  the staute of limitations on prosecuting your boyfriend in most states for having under sex, if 5-7 years.  I suggest that you make an appointment to meet with a laywer that can tell you for sure the age of consent in CA.  you should also ask the layer to confirm the statute of limitations for the state's right to prosecute your boyfriend.  Most lawyers will meet with you and provide you with an initial consultation for free.

The age of consent is 18 in CA.

Anyone who engages in an act of unlawful sexual intercourse with a person under age 18 who is more than three years younger than the actor is guilty of either a misdemeanor or a felony.  It is punishable by up to one year in a county jail or by imprisonment in the state prison for two, three, or four years.

This offense is aggressively prosecuted in CA.  Before you do anything else, speak to an attorney in your area who can more fully explain your situation to you.