OK so. First thing tomorrow you get a test from tesco. You can find the privacy to do it, just run the shower. Or say you are having a nice long soak. Whatever the routine is in your house.
Doing the test doesn't change what is, it just kind of brings you into the next stage of what you need to think about. I know it's really hard, you sound quite together, and sensitive to your mum's views. However. She is your mum, and that means she is there for you thick and thin. So think very carefully before you go ahead and do the next thing.
Scenario - you test positive, you're pregnant, is not just a bad reaction to a new pill.
You seem to say you don't want to start a family just now. That's OK. It's your choice. But do make sure it is your opinion, not other people's. If you are pregnant and you decide to terminate, you should consider this : how does your bf feel about it? And will he support your decision, because if he doesn't, you will need your mum all the way. Which is why I'm advising thinking carefully about keeping your mum in the dark.
You're not 16. You are a responsible adult (although this kind of situation makes you wish you were 12 again and had no other worries than what the number one was this week) That means you have the right to stand up and say what you want to do about your situation. But you need the information to do so. So my advice is this.
Do the test.
Find out how to terminate ( speak to gp, then Marie Stopes)
Then, armed with information, talk to your bf, and then, your mum.
I really feel for you. You're not the first and you won't be the last. Just, make sure you know exactly how you feel before allowing everyone else to weigh you down with their opinions on what you should do with your life. Including the anti-choice brigade.