Trying to fix things with my husband

Me and my husband have been separated since June. A long while ago I talked about how I'm going through infertility and we have been trying for a baby. My husbands 18 year old sister got pregnant and was gonna marry her baby daddy and his parents were paying for the wedding. I was mad she was pregnant and mad at his parents for paying for it when they could be saving the money for our future baby. I didn't want my husband to go to the wedding but he was his sisters best man and said he has to support het and I don't have to go. That pissed me because I'm his wife and he should pick me. I decided last minute to go and seeing her show off that tiny bump in her wedding dress pissed me off. I did and said some unforgivable things that night and pretty much ruined her wedding and my husband left me the next morning. He put his ring on the table and said he can't be with someone who thinks its okay to treat his little sister that way and do the things I did. He's been staying with his friend since June and he's finally agreed to speak to me about our marriage. I need to save my marriage and need to know how.