You're right to get checked out. It could be anything.
Here's some questions for you to ask yourself. How long have you had it? Is it more obvious at certain times of the month? Is it in the same place
all the time?
This is the reason we are now taught to be "breast aware" rather than just examining ourselves once a month. By knowing our own bodies we can easily
notice any changes.
To answer your question- no, you don't necessarily get a discharge with cancer, though if you had one, or if your nipple is inverted or mis-shappen,
that could possibly, but not always, be a indication of something more serious.
Please don't panic too much. I know its not easy (I've been in a similar situation). Even if you have a lump, the greatest majority are benign. If
the worse should happen, breast cancer is now one of the most treatable.
Here are a couple of links.
It must seem like a long time until your appointment. Please u2u if you want someone to talk to.