While I'm hooking up with them they usually tell me I can have any girl I want

Another thing they say usually before we start hooking up is you're not getting laid tonight

This is halfway between a compliment and a mild shit-test. When a woman says that, she expects you to say "You are the woman I want". That would place you in pole position for the BF title. I gather that you want only the hookup, so avoid this answer. Responding in a smiling and confident way "Thanks" or "I know" is one way to defuse the situation. Another one would be to smile in a mysterious way and change topics.
This is girls rationalising what is happening. The next day she can lie to herself and her friends "I told him we're not sleeping together but we somehow got carried away". I respond with "You have to take me out to dinner and a movie before" turning the table on her. This answer gets them laughing and takes the edge off the situation. The "we're not sleeping together tonight" line can be also seen as a shit-test checking for any disappointment or angry reactions from your side. Play it cool...