Jealousy and demisexual/demiromantic feelings

I have never fallen in love in my life, but sometimes the thought of certain friends falling in love with others and engaging in relationships with them makes me a bit jealous. I feel like these friends with whom I have a strong bond, a strong emotional connection, are potentials "love of my life", and even if I haven't really fall in love with them, when they engage in a relationship or shows interest in someone else I feel like I have lost an opportunity to make a move, but how could I ever make a move? I'm not confident enough to do that and I also don't want to lose a friendship.

I have this long term friend, once when we were teenagers he showed interest in me, he even said that he loved me, but at the time I couldn't reciprocate, I was entirely focused and other things in my life and maybe my low self esteem didn't allow me at the time to believe that someone could actually like me and want to have something with me. We are still friends, we have a strong bond even though we don't talk too much. I frequently have dreams about engaging a relationship with him, of being really romantic with him, but he's living in another city to study right now, and makes me anxious that he could find someone in the city is living at, and obviously he has all the rights to fall in love with someone else, but the thought of it hurts me. Last time we talked I tried to show a little bit of interest in him, but always showing it in a "friendship" way, like, "oh when you're coming back to the city we could do something together, to celebrate the old times, celebrate the friendship of 14 years that we have". I'm not brave enough to recognize that maybe I could want to have something with him, but I am not even sure of that, am I really interested or I just want don't want to lose an opportunity cuz being demisexual is so hard when it comes to romantic relationships? I don't want to try something to then discover that it wasn't really what I wanted and end up ruining the relationship and hurting him.

Have some of you experienced it something like that? Let me hear your thoughts, I'm looking for some advice too, what should I do?!