Who hates being left out?

Does anyone ever just feel left out? Like you don’t have many friends even though you talk to(or don’t talk to) many people? I feel like all throughout my life I’ve been left out of things and I have no understanding of why this happens. Is it because I don’t like showing people my emotions because it makes me feel weak and vulnerable? Am I too clingy? I’ve constantly been told in my teenage years that they didn’t invite me because they’re parents said they can only invite a certain amount of people. I’ve had peoples parents not like me for whatever weird reason. I’ve introduced people only to have them start hanging out without me. I just wanna know why people can’t tell me to my face why they’d rather not spend time with me so I understand and adjust.