And in claiming there is, you are telling on yourself about the fact that you consider sex to be purely transactional and even more than that, something you "give" to the man.

Sex is something two people do TOGETHER, and just as they say women in relationships do not owe men sex: conversely men having sex with women do not owe women relationships.

If you feel like a guy is "stringing you along" then don't have sex with him, if you do, don't turn around and call it being "used."