Yes. While it may feel uncomfortable for a short moment, it is important that your attorney have complete information so that your interests can be fully protected. If speaking directly about these facts still seems too hard, consider putting them in a letter.
Attorneys who practice divorce law are accustomed to hearing a lot of intimate information about families. While it is deeply personal to you, it is unlikely that anything you tell your lawyer will be shocking to him or her. It is much better for you to tell your attorney this information early on, rather than your attorney finding out later in the case (possibly from your spouse’s attorney), when your attorney is less able to incorporate or at least plan for the “surprise” information quickly during a court hearing. Most issues can be “fixed” or at least improved if an attorney is given enough lead time to develop a strategy.
Your attorney has an ethical duty to maintain confidentiality. Past events in your marriage are matters that your lawyer is obligated to keep private. The reason for this ethical duty is so that attorneys’ clients can be more comfortable in sharing all relevant information so the lawyer can better represent his or her client.