I think you need to take control of the situation by letting them get on with it and fading them out of your life. If that means muting them on Facebook so you can’t see their posts or ignoring their texts then so be it.
Without knowing the full story it sounds like something has happened and one of your “friends” for some reason no longer likes you / outgrown you and the others have followed like sheep hence the evening where they talked over you and disagreed with everything you said and made you feel uncomfortable.
Although I believe it is fine to meet up with friends and not always invite everyone, if they are ALL meeting other than you then I think the right thing to do is to forget this friendship group.
Although you might have to fake it until you make it right now, taking control of the situation yourself is going to make you feel better in the long run. You can leave the friendship with your head held high knowing that you were the one that walked away from these horrible friends.
Making friends is incredibly hard, I’m 31 and it can be a struggle but it is better to have no friends right now then six fake ones or however many of them are there.
Make an effort to join baby groups and get chatting to other parents, I do yoga once a week without my child and get talking to other people there. Perhaps there is a hobby that you could take up that will get you out around other people.
Don’t feel silly making conversation first, a simple hi I’m new here and I don’t know anyone, what’s your name? Could spark a friendship.