I know I'm a jerk - but just please give me an opinion on what to do? (rephrased question)?

I'm 31. I'm dating a woman who is 33 for about the past 6 weeks. She is nice and we seem to mesh well. We are involved physically. It started as a casual relationship - friends with benefits, if you will. So age didn't really matter much to me. I actually wanted to learn from her experience. She didn't initially want anything serious either. But we seemed to get along so well, that it morphed into something more. It's just a little scary that this whole relationship sprung out of nowhere and was so unexpected. I've learned my lesson about friends with benefits - no such thing! and bad idea! But now that it is something more, I'm facing the fact that she is not the person I imagined myself with. I always imagined myself with someone younger and with whom I could spend a few years before having kids. With this lady, I would have to have children right away. Also, her mother has a chronic illness that would require a lot of care from her. I am very conflicted about her, and can't seem to let her go, but also have trouble committing. There are other younger women out there that I know are interested, but I feel bad dating more than one woman at a time at this point. Should I force myself to do it, knowing that I'm taking a chance of ruining what I have with this woman? I have talked to her about the fact that I may date other women (and necessarily back off from the physical aspect of our relationship), and she has grudgingly accepted. But I know that if I do, it may stunt this relationship.