I feel abandoned by my son's friends and their families.
That's too bad. Why do you feel abandoned by them?
I was so happy when they were around my son, but now they almost never come to my house anymore. It feels really lonely at home sometimes.
I understand that you feel lonely for not having people around. But you should understand that your son's friends also have their own families so it's understandable for them not to spend time with you.
I'm afraid my son will start spending more time with them and less time with me.
I doubt that will happen and I'm sure that your son loves you very much. Have you told your son how you feel? He'll probably be happy to schedule a visit with you.