<human>: Can you condense the text into three sentences or less?

My girlfriend and I have been together for 3.5 months now. The first two months were fantastic: very fun, exciting, and really everything you could want in a relationship. Everything happened quite quickly between us. We starting holding hands affectionately by the end of our first date, and exchanged the "love" word after spending nonstop time together for a month. Even now, I really respect her as a person, and find her intelligent and attractive.

But about a month and a half ago, I realized that I stopped going out of my way as much to talk to her and spend time with her. After she confronted me about this change in behavior, I told her that it was due to me needing more alone time for myself, which she completely understood (she has somewhat of a history of issues with mental health). As of the past week or so, I have been nonstop thinking about what a relationship would be like with someone else. There is no one person in particular, just other nice women that I meet in classes and life. I still find my girlfriend to be a fantastic person- she is very driven, kind, and understanding. But at the same time, she isn't as exciting to me as she used to be, doesn't challenge me individually in ways that I would like a relationship to, and doesn't attract me as much as she used to.

Is it immature of me to be thinking of relationships with other women? Am I being disrespectful to my girlfriend? Or should I think of ending the relationship with her solely because I've lost interest?

Thanks for any advice in advance, I greatly appreciate it!
<bot>: Have lost some interest in my girlfriend of 3.5 months due to thinking of relationships with other people: is this me being immature, or a sign I should look to end the relationship?