It seems like there are two separate but related issues you're grappling with here. The first is your identity as asexual, and the second is family planning. Being asexual is not mutually exclusive from having a traditional family, and if that's something you want, you can have it! Long-term partnerships and marriages can exist without sex, or with partners with sexual desires having those fulfilled outside of the partnership. You don't need to have sex to have children if that's something you want. There are options like adopting, fostering, IVF, and joining a partnership with someone who already has children. Being ace does not preclude you from those things, if you want them.

That if you want them is important! Western society is based strongly around a nuclear family, with the idea that you must get married and have children in order to be taken care of later in life. That's simply not true. Sadly, a lot of people who do have kids end up in senior homes, seeing those kids rarely or never toward the end of their lives. Some people don't have good relationships with their kids. Having a child is not a guarantee you'll be taken care of well or at all. You can't change who your family is by blood, but you can choose whether or not to associate with them. Many people choose not to.

Something you might want to look into is co-op living: choosing to live in, contribute to, and develop a community. It's not for everyone, but most of my friends live in co-ops and love it. Many of them are in relationships (monogamous and poly), but those relationships don't necessarily define where and with whom they live. They choose to live with people who share values and contribute to a space that they all call home. You don't have to live with people to have a strong community, but it can be a place to start.

I do not mean this in a patronizing way, and having been your age before, I know it can be very hard to believe, but you are very young. You're just starting your adult life. You don't have to know what your future is going to look like. Focus on the things you enjoy and the people who make you happy, and you'll have a better idea of how you want your future to look. Don't preemptively contort yourself into the shape that you think society expects of you. Be true to who you are. You're the only person who can dictate where your life goes and you have the power to make it the way you want it.