As a 26 year old female, I understand where you're coming from. I've also decided to wait after marriage when it comes to having sex. I've only dated guys that I am interested in genuinely and may see a future with them, otherwise I don't really date. I've never been tempted to just have casual sex as I am also a stubborn and strong willed person. Its great that you have friends that are from different religions/atheist but don't worry about what others are doing and focus on yourself and your relationship with God. There are other ways of having fun in life and not everything is involved in dating and sex. Sometimes I remember this quote and realise God is more important than a few minutes of pleasure. Mark 10:6-9 - "But from the beginning of creation, ‘God made them male and female.’ ‘Therefore a man shall leave his father and mother and hold fast to his wife, and the two shall become one flesh.’ So they are no longer two but one flesh. What therefore God has joined together, let not man separate.”