phone gets hot on 3g

Yeah mine gets nice and toasty sometimes especially when downloading or using Pandora or I Heart Radio
 
If I download a batch of podcasts over 3G mine gets pretty warmish as well. Usually eats battery too.
 
Could be your OC. Obviously higher values will produce more heat, and with a steady stream of data you phone will be maxed out to whatever you have set most of the time in use.