Ok, deep breaths. Remember you absolutely do have a choice and time to do something about it if that's what you decide.
Are you feeling sick? Even if not, early pregnancy hormones can be really difficult and make you knackered and emotional. Nothing wrong about that, just something to be aware of as you try to work out how you feel.
You can ring BPAS and ask for pregnancy counselling - someone non-judgemental who can help you find your way to a considered decision.
For what it's worth I felt exactly like this. Pregnancy wasn't planned and I was really, really frightened and weirded out when the test was positive. It's a massive life change if you go ahead with it.
Then I spent eight months with my head down the loo feeling rotten
I couldn't have been further from the 'blooming pregnant woman' stereotype, i was a mess all the way through.
This was 18 years ago and I had another one two years later. They're absolutely the joy of my life and I wouldn't change it for the world. I really can't express the massive love and purpose they've brought to my life (even when they're being awful)
BUT this is your decision, and it's entirely in your control what happens. But yes, I'd say feeling like this is entirely within the bounds of 'normal'.