<human>: I've had a few long term relationships before, and this keeps happening. We fall in love, everything is perfect, sex is great, but after a while (a few months, or a year) I just lose interest. I only fantasize about other girls, sex just doesn't interest me anymore, etc. This kills the relationship after a while.

It has happened with my previous GF as well. We were together for 4 years. She was perfect, sex was great at first, we were living together, but I slowly lost interest.

After the inevitable breakup, I have met my current GF, Lisa. I was in love, like never before. After we started dating, for months I couldn't think of anyone else, the only girl in my fantasies was her. I have never felt anything like this before. And I was terribly afraid that it's going to happen again.

Now we have been together for more than a year, and I am starting to feel like I am losing interest again. I don't want to lose her. She is perfect for me. But I start to feel the same things as with my ex - losing interest in sex, fantasizing about other people, and so on. Even my fear of losing interest is making me lose interest, if this makes sense.

I don't want to lose her, and I am afraid that there must be something wrong with me. What do I do?

Give me a shortened version of the text
<bot>: I keep losing interest when in long-term relationships. What do I do so that it doesn't happen with my current GF?