I feel like a sl*t....

Long story short, he cheated on me last September so I divorced him. I have been out dating since the end of December. Never slept with any of the men I went on dates with. On New Years eve I went to the bar and had a few too many drinks and had slept with a man I really knew nothing about. I know it's terrible, but it's crazy what a divorce can make you feel like. I have been working 60 hours a week and forgot to take my pill or took it late a few times. Well, I ended up missing me period and am now pregnant. I know this mans name and that's it. I will happily raise this child on my own but how do I bring this up to people when they ask. I am in the process of finding this man but am EMBARRASSED to know end. This is not ever something I would do. Please no harsh words, things happen, it's life. I made a "mistake".