The relationship you need to be working on right now is the relationship you have with yourself. You got together with your ex when you were only 16. You’ve never had the time and freedom to explore who you are independent of a man. It doesn’t surprise me that you come off as needy and dependent. It’s very possible you are looking for the guy to fill in the blanks of who you are.
The healthiest relationships are made up of two people who are strong, capable people who like themselves because of the many ways they contribute to the general good in the world. They don’t look to a relationship to “complete” them. They are already complete and enjoy their own company. Such people look for an equal partner in life’s journey.
At 18, you have lots of time to find a boyfriend. Drop the boyfriend search. Focus instead on making friends and on doing things that help you feel good about yourself. Join in on some of the many activities available on campus. Get involved in community service. Get engaged with your studies. Be the kind of student who asks interesting questions and helps a class be exciting. The romance will eventually naturally follow. If you want to find a healthy relationship, you have some personal work to do first.
I wish you well.