Am I overreacting?

Hello, first time Mum here. So my baby is 4 months old. My boyfriend and I usually switch nights for who wakes up to get her if she fusses. I've been sick all week and on his night I woke up to get her because he wouldn't. I'm obviously not going to leave her in distress, so I dont mind getting her. My issue is that my cold has taken a turn for the worse and I needed medicine. He picked me up some nighttime cold pills, but I told him it was technically my turn to watch her and I'd probably be in a deep sleep. He looked at me and said "Don't worry, I'll wake you up". I feel like he's just so selfish. I dont know why it upset me so much.