My heart goes out to you, and sometimes it can feel so isolating. There are a lot of positives being an only child. You have no huge arguments with siblings and hopefully you are not competing to get the attention from your single parent?
If you are at school, try to feel the love and care from other families when you visit friends. There will I am sure be many other parents who recognise it can be a lonely place without the surround of family members and do all they can to welcome you into their households. Sometimes the 'cared for' feeling can be a little elusive but you still have one parent, and hopefully still feel a lot of love.
As you get older you can find people who offer you the feeling of constant love and care and you can join their extended families. You can adopt a family, adopt a Granny or elderly person and make sense of the world by giving care to others. Hopefully anyone you meet will have lots and lots of relatives, cousins, siblings and you will be absorbed into the mix. Everything can change in life and sometimes you just have to take a day at a time. Be so glad of a warm dry place to stay, food and support, and education, even though life might not be perfect