Lonliness

I'm 40 with 2 children, partner works away which is fine as we agreed on this. But friend wise, I feel lonely. I mean I have people I'm close with but since my birthday I've realised that none of the friends who I thought would make an effort made any effort to celebrate with me but yet I would go out of the way to celebrate theirs. I've always been a people pleaser but I'm fed up and it's made me realise I want to be loved by my friends and not just someone they can use and chat when they feel like it. I've always been a good friend, but why is it hard to maintain a friendship as you get older. I just need to vent