I got to level 15 and now it is doing that and every match i play doesnt give me xp or money
Your problem is different. I assume you're using the Free to Play version of Uncharted 3. When you hit level 15 in Free to Play, you stop getting anything. You don't level up, you don't get cash, you don't get wins. You have to buy the level cap add-on to earn money at level 15 and above.
How do you fix it
If you're playing on Free To Play, you need to buy the level cap add-on.