How to talk to boyfriend about certain things!

me and my boyfriend are getting along great and will most likely marry in a few years--we are both Christians---the past few days he has put his hands in places that I am uncomfortable with since I don't really feel that kinda thing is right before marriage--even though it isn't sex--I just feel insecure about it at this time---I want to explain to him that it isn't b/c I don't like it but that I just feel it is wrong to be doing this kinda thing at the current time--I don't want to be harsh or cruel or anything like that---just want him to know my personal feelings---how should I go about this? Tweet