Did I do something wrong?

My fiancé and I are going through a really rough patch right now and it’s escalating quickly. I don’t know what to do anymore. We’ve been fighting for the past few days and today he left pretty upset. So last night we got into another fight and I decided to leave to the gym. On my way back I was coming down the street where my best friend leaves and thought would stop by and say hi real quick. Nothing else since I haven’t seen her in while. Cause we’re both pretty busy. She wasn’t home but she was at work and her job was on my way. But before that she tells me she’s working alone and she’s really hungry and thirsty and can’t leave, if I can please bring her something. Now I felt obligated, how could I leave her to starve? So I said ok. I stopped by Burger King took her burger and soda and I literally stayed for about 5 minutes and left and told her my fiancé was home alone with the baby so I should take off. So I take off and get home. I didn’t tell my fiancé this as he clearly didnt want to talk, he even went and sat at the dining table to watch tv when I sat on the ground with him and the baby. So why should I tell him? Was I wrong for not telling him or calls him that I was going? I mean I wasn’t hangin out, I was just dropping some food. Now, he thinks I didn’t go to the gym and that I just went to hang out and im a shady bitch for not telling him.