In your situation you have to be kind of proactive. I made it a point in the past to be active in the community, volunteer, work, church, join groups, accept invites etc. Then I went through a bad period and it all fell away. I was surprised. I didn't know I had been putting effort into staying connected until it was all gone. While you are still young and your parents are alive you could make an effort to get connected in your community. Your fears are not unfounded. Without effort one day you could find yourself quite alone.

People with big families also feel lonely, too. Sometime they just see family members on holidays, but daily life is lonely. I am making a New Years resolution to reconnect. You will be surprised how much can happen in a year if you make this a goal.