How can I help my boyfriend get a aggrevated assult case dismissed against me?

Based on what you wrote, it appears you are the listed complainant. What you can do to help him is hire the best attorney you can afford to hire. Additionally, you are free to call or go the DA's office, and try to explain it to them. But, beware: if you do not have a complete understanding of the law as it relates to assault, you may do more harm than good by speaking to the DA's office. In my experience, complainant's who try to talk the DA in to dismissing an already-accepted charge are often manipulated into confirming the allegations, which will undermine your attempt to get the case dismissed. So, like I said, you need to be very careful. If you want to be safe and smart, help him find a good lawyer, and the three of you can discuss the facts of the case, the law, and the best way to proceed, in light of all three.