BAD SAT Subject Test :( Help!?

I recently got a 660 on the Math Level 2 Subject Test. Ever since January, my SAT scores have been dropping and I'm really beginning to lose confidence. Do you know how much SAT subject tests affect college admissions if I'm looking at top schools (e.g. Georgetown, BC, Notre-Dame, Johns Hopkins)? My SAT scores would be my downfall. I would really appreciate it if someone could help me out :(