I feel like my longtime friends are leaving me out. How can I get more involved?

If you see them every day and meet every Saturday exactly how are you being left out?

Start concentrating on the individuals within the group. Invite them one at a time. An overnight at your place. Going out with your family for pizza or a burgers invite one along. Go to the movies invite one along. Invite one to dinner and a movie at your place. Increase and strengthen your individual relationships.

I would not confront them because if you challenge people it could go a number of different ways and one of them might be to make things worse or make people start denying instead of being honest. So I'd only do that as a last resort.

Good luck.