How do you know if a cartilage piercing is infected?

I got my ear cartilage pierced about 5 weeks ago. It's still sore, when I touch it or lay on it. Also, if I twist it around sometimes clear liquid comes out. It feels almost like blood, but when I touch it, nothing comes up on my finger. What do I do if it is infected? I really don't want to take it out. It is almost time to switch the earring anyway. I've been cleaning it with a sort of contact solution with saline solution in it. What do I do? Also, how long do I leave the first earring in? I have heard 6 weeks and I'm heard 3 months.