The first step to overcome any fear is to identify the cause. In your case it might be because of watching your parents fight or, having someone close who has suffered abuse in a relationship. With this you can recall when you started getting scared about romantic relationship.
Just they way you feel insecured when introduced to strange activities, allowing someone into your life for the first time might be scary. It doesn't mean you have a problem. It does mean you have a natural defence intuition.
1. Start to learn more about your likes and dislikes. Continue to be who you are and try to display the best quality of your unique self. This way you can be assured that you're attracting the right people, keeping away from possible bad experiences.
2. Deciding to start a romantic relationship should be based on personal feelings and desire. Not because the crowd are doing it. Not because your best friend is good at that. Live above your comfort zone. Be confidence of where you are now. Do not take a drastic change.
3. Never go hustling. Do not just look for someone to hook up with, it's a wrong way to start. Be in a relationship with a partner and a friend, not with someone you WISH to be in a relationship with. Even if you're the last that has never 'been in a romantic relationship' among your friends, rushing into it without making a rational analogy of things around you is very dangerous.
4. Start a relationship with a good friend. Be patient and don't be afraid of pains.
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5. Understand the difference between healthy and unhealthy relationships. Because the latter might ruin you.