I know what you're going through. Everyone around you has this plan for their lives. They know what they want to do, what they want to go to college for, what job they want. They know what they want their future family to be like.
And meanwhile, to quote Phoebe Buffay, you don't even have a "pleh."
I know you because I am you. I came into college undecided, declared a major, and then switched it my first semester of junior year. I like my new major, but don't know what on earth I want to do with it.
I was never someone who could envision her future. I couldn't even imagine what I wanted my future wedding to look like, and quite frankly, I still mostly can't. Sure I have ideas for little things, but nothing about the big details. To me, the future always looks like a big black gap.
And guess what? It's not the end of the world to not have a plan. It can be good to just take life as it comes at you and make short-term plans as they're needed.
Not having a long-term plan or vision of the future means you aren't setting yourself up for disappointment or failure. You don't have a mental standard to live up to or plan to stick to. No plan means you won't feel that upset of "I'm not where I wanted to be in my life plan by now."
Does it suck to not have a plan, not to know, when it feels like everyone else does? Of course. It's also incredibly stressful and pressuring.
But just remember that it's okay not to have a plan, or even a "pleh." Learn to take life as it comes, make those short-term plans, and your life plan will eventually piece together in your mind--and in your life. Take things one day, one week, one month at a time, and don't worry too hard about the long-term things until they're relevant. You'll be okay, even without a major plan.