How to get nukes easier on mw2?

i have been trying for about 12 hours of gameplay to get a tactical nuke. i always come close but then some queer spams me with concussion grenades and or snipes me. my highest killsstreak is 19 i believe and i didnt use a harrier or pavelow. i use predator and emergency air drop and nuke. i is level 37 no prestige. anything will help.