Friend issues, does this ever bother you guys too?

Okay well im 16, going to be a senior in high school. My two best friends and I used to hangout all the time with all 3 of eachother. Now we all work, so its hard to mix schedules, but it always seems like they can get together while i work, and then theyre busy when im free. Other times im free and they are and they hang out and dont invite me, yet other times i hangout with one of them instead of both. Its weird and I don't want to sound like a little kid by saying this, but i feel very left out since it's summer and days im free, they are out hanging out and don't seem to invite me. Now i obviously have other friends i can ask to hangout with no problem, but it just bugs me how we always say we're the 3 closest friends and they take all these pictures and stuff and when its the 3 of us we never do that. idk is it just me? hahah sorry for rambling