I had a terrible thought...

Hello I need some advice and comfort. I feel just terrible... I don't know what's wrong with me. A few nights ago my daughter was crying and I was so tired. My SO was asleep because he expects me to get up with her at night because he works. I felt so worn out and angry at him. My daughter kept crying and for a split second I thought what if I lay her on her stomach and she suffocated. I immediately felt terrible. I went to the bathroom and washed my face to cool down and gather my emotions before I went to tend to her. I can't believe I had such a bad thought. I feel like a terrible mother.