Ok. I am 17 years old. I live in ohio. I have been dating my boyfriend for a year and a half now. He is about to turn 21 in July. I wanted to know if my parents could press charges on him?

Yes, they could file a complaint against him; however, he would likely not be found in violation of the sexual offense law listed below given the fact that you are over the age of 16. There is a possibility he could be in violation of lesser offenses that would not be sexual offenses.

A parent has full legal authority over their minor child until that child reaches the age of majority (18). They are within their rights to take legal action through an attorney or the authorities.

§ 2907.04. Unlawful sexual conduct with minor.

(A) No person who is eighteen years of age or older shall engage in sexual conduct with another, who is not the spouse of the offender, when the offender knows the other person is thirteen years of age or older but less than sixteen years of age, or the offender is reckless in that regard.
(B) Whoever violates this section is guilty of unlawful sexual conduct with a minor.
(1) Except as otherwise provided in divisions (B)(2), (3), and (4) of this section, unlawful sexual conduct with a minor is a felony of the fourth degree.

(2) Except as otherwise provided in division (B)(4) of this section, if the offender is less than four years older than the other person, unlawful sexual conduct with a minor is a misdemeanor of the first degree.

(3) Except as otherwise provided in division (B)(4) of this section, if the offender is ten or more years older than the other person, unlawful sexual conduct with a minor is a felony of the third degree.

(4) If the offender previously has been convicted of or pleaded guilty to a violation of section 2907.02, 2907.03, or 2907.04 of the Revised Code or a violation of former section 2907.12 of the Revised Code, unlawful sexual conduct with a minor is a felony of the second degree.