Shocks n Springs Q. Help.

hi. im a noob at this car mod stuff so i need some help.
is there such thing as the shocks are too tall? im trying to lower my car and bought ractive coil over springs and installed them, went down like 2 and a half in. then test drove it, but it felt like my car had no springs nor shocks. my car was jumping up n down on the smallest road bumps. so now im planning to buy yellow konis. are them konis low enouhg to work? im just confused because people told me my stock shocks will work when i lower it.