I’ve been feeling extra lonely

I've been feeling extra lonely these days, can someone tell me why? I've dealt with this feeling for over a decade now but at the moment it just seems unbearable. I've been craving affection and attention like mad probably because I've been receiving it before and now that I don't, I crave it more and more. It's making me sad as I realise I've been receiving not from the right person. And I'm not sure if I can do anything about it.