What should I do, I am eighteen and maybe pregnant, my mum doesn't know but is extremely upset about the idea?

She will change her mind once she sees the baby. I think she just doesn't want this right now for you and for the baby and for maybe how it looks to other people. I'm not saying the way she is acting is right. If you are pregnant than she shouldn't act like this, because there is nothing to do about it. You are an adult, you can make your own decisions about what is right. I would suggest having your baby, you sound like you want to. Otherwise there is always adoption, or a family member could watch the baby. Don't feel too bad, she is just freaking out about it, she should calm down later. If she doesn't, than I would suggest moving on and away from her negativity. If you aren't pregnant though. Try to go to finish school and build a foundation where you can provide for her, because having a baby will make that extremely difficult.