I think I might be pregnany? How can I tell before the test?

[possiblyprego]

I have talked to my step sister and I think I might be pregnant.

Some signs I have are:

weird discharge for the past month
lower abdomin pains at one time in the day every day
nausea
the feel of pregnancy
severe mood swings I didn't have before
back pain

I would like to know if I need to worry about possibly being pregnant. I'm worried because I am only 16. Please let me know if it is something I need to worry about, and what kind of chance there is that I am for sure pregnant.

-Possiblyprego