How to get better at MW2 online?

About 3 days ago, I was the king on MW2, I was ending games with 31-9, 20-3 and 13-0. But today, my best games have been 7-10, 8-12 and 4-12. WTF has happened? I play MW2 everyday and I use Scavenger, Hardline, Ninja, Stopping Power and Sleight of Hand (All pro) and I'm still dying before getting Care Package. Whenever I spawn, I move 3 metres then get stabbed in theback by a runner, quickscoped by an 8-year-old or sprayed with ACR. I use the best guns, but I'm still dying. Any pros got some good tips?