Hi William,
I think you're suffering from low self esteem. Are you a shy person? The reason I ask, is I was very shy when I was younger and it held me back alot. You have to learn to not listen to the critical voice inside your head, because he is your enemy. As the saying goes "it is far better to try and fail than to not try at all". There is a match out there for everyone. The reason why it's bothering you now is because you're getting to an age where you're questioning the path you've chosen and you see others with partners and families. Would you like to have children one day - they're awesome. Shyness, social anxiety and self esteem are all managable issues. You don't want to look back and regret not taking the plunge. Don't worry about rejection - sometimes girls reject guys because they're struggling with their own issues. I also think you trying to protect yourself from heartache, but you know we've all been there -sure it hurts for a while. We just get back up, try again and learn from our mistakes. Believe in yourself. Good luck.