I do want relationships, something that will last and someone I can love, but, anytime it comes close to me getting into one I just suddenly lose all my feelings. I no longer feel like it is something I want to pursue, even though, a second ago I was gushing about him and thinking about a happy, loving relationship. Relationships, I rarely get into, an even if I do, they are short-lived. It is like I just convince all my feelings to leave me and take all my pessimism and let it savor my love life.
To make things worse, I have someone and we can turn into something more. We had a nice day and, somewhere along the way I am already not sure and when I am back home, I am already into thinking it was a mistake to lead him on.

How old are you? Sometimes young people WANT a relationship, but find that the level of interest in that person was never that high in the first place. The IDEA of romance drives the feelings, but the reality is that it just ain't that simple. Dating is having fun getting to know someone, not a relationship interview. It's not unusual to have feelings while with someone, and they fade when you are NOT with them. How long have you been dating THIS person?

I believe your feelings are telling you to slow down and not get ahead of yourself. No you cannot just find ways to hold your interest for another, and it's a big red flag when you do. While its great you are not afraid to take a risk, and explore and experiment, keep it real and recognize you just have not met the one who can hold your interest. That doesn't mean you don't like this current fellow, it just takes more than a warm willing body to make a relationship beyond the fun dating. I think part of your problem is that you don't want to lead these fellows on, but just being honest and not second guess yourself so much could help.

There is no shame in losing interest, for whatever reason. The shame is not being honest about it. Everybody wants a love life, but forcing it or pretending interest is NOT love, no matter how it great it looks on paper. It's selfish and hurtful in the long run. Most young adventurous people have fun dates, and make many fun friends, and enjoy many connections that just don't last. The trick is don't get down about it for long, when clearly it's time to move on.

If you are losing interest.. that tells me that its just not right and they REALLY aren't the one. It's a huge mistake to make do and settle, you are far better off to just keep looking, eventually you will meet the one... and you won't lose interest in them early on, or even later on, and eventually you will know they are the one for you. It won't happen fast, or quick, and they might be the last person you expected at first.

You may feel being alone sucks...but it sucks a lot less than handing over half of everything you have left after paying the lawyers in a divorce when you get sick of being with each other after you acted too fast. (not actual experience, just based on a lot of friends who have)