sam - have you got someone who could drive you to the hospital, and make sure that you go? There is absolutely no point in trying to self-diagnose, you need that scan - as others say, it may not be cancer (there, I've said that word), it could be other conditions not difficult to treat.
You were courageous enough to see the GP - well done - now go that next step, don't waste the scan appointment. You are not alone, hundreds of women have been scanned each week, so please go for the scan. If there is anything unusual, you can be treated - if you don't go and it turns out to be serious, you'll not be helping anyone by not going at this early stage. Let us know how you get on.