How can I tell my mother I'm pregnant?

This is hard news to hear for a mother, especially if you are young and unmarried. The setting is just as important as the message. I suggest picking a moment that you are both calm, early morning or early evening after a non-stressful day could work. If you can manage it, take her out for dinner; it's neutral grounds and she would not want to make a scene so she us less likely to erupt at that. Tell her you know she might be disappointed, but you really need her strength and support at the moment. She'll most likely be upset at you, but she'll have your back. And you can reach out to the 7cups community if you need more support.