Are You Stuck in an Emotional Puzzle?

I’ve been dating Tina, my girlfriend, for about three years. She’s the only person I’ve shared a long-term relationship with, and I simply love her from the core of my heart. But, the only thing that scares me is that I might be losing interest in her.
It really breaks my heart even when I imagine that how much it will hurt her to find the fact that I don’t enjoy being with her as much as I did in the initial phase of our relationship. I mean we’ve been dating for so long and I know I just can’t live without her. However, everyday I get up in the morning and I get pissed off with her. She’s a couple of years elder to me and says that her feelings are as strong as it was the very first moment she fell in love with me. I’m really surprised how some can sustain these feelings and spark for such a long time. Well, I won’t lie and say that I don’t look at other women and think of how dating them would differ from dating my current girlfriend. on the other side, I can’t break up with her just because I’m tired, we’re so much into each other, we live together and even have a dong. Nah, it wouldn’t be fair to her. Well, I’m trying to find was so that I can revive and rekindle that burning fire and get that feeling flowing again.
It really hurts me to even imagine what would happen to Tina if I left her, I can’t do cuz I love her to bits. We’re so embedded in each other’s daily routines now that we rely on each other to help us get through the day. But, after dating for so long, at times, I find myself wanting more, wishing I was dating other women and not just anyone, and leading an exciting lifestyle out there in the world.
Well, I’m expressing myself here just to vent those pent-up feelings and frustration. Well, I guess I need to try and get that fire burning again. Probably, that seems to be the solution. Maybe, it’s time for me to stop taking our relationship and our life together for granted.