Its not your job to make every female in the world feel happy and secure. It ain't guna happen. You're guna piss people off at some point. You can't avoid it.

You should just be honest with yourself, and honest with the girls. Do you even WANT a relationship, or do you wana play the field? If the latter, then tell them from the beginning that you don't want anything serious.

Edit: Men don't always like it when women reject us, yet women continue to do so without giving a shit? Do you see them feeling guilty about falling for two guys?