please learn the word NO and practice saying it till you are confident to use it, until such time steer clear of any situations where there is any possibility of these sort of things happening!
if you don't want sex or handelling in such ways you describe then say NO firmly, it is the only way to be sure, saying NO firmly will either result in the guy backing off preventing a rape, or the guy will continue just as he would if you had said nothing, only difference is your saying no means he was made aware you did not consent and giving you the crucial thing you need to prosecute for rape.

please for your own sake learn to say No!