In college, it is common for people to think that you have a definite plan. That is the point of college, after all. However, it is okay to be in college and to be lost. Not everyone completely finds themselves in high school.
There simply isn't a set time for when people know exactly which path to be on. Things change every second of every day, so plans are constantly changing. Being lost happens countless times in a lifetime. If you feel as though you have to have it all together, then don't.
There may be a time where you want to change your major or even just drop out of college totally. You're not alone. The best thing to do is to take a deep breath and find someone to help guide you. College is an overwhelming time. The pressure to be the best and to be the quickest one to graduate can get to anyone. But it's no contest, it is completely okay to be lost and to doubt your plan.
If you already set a concrete plan for yourself, it doesn't mean it's the one you have to abide by. Take a bit of time to catch your breath. You could even embrace the fact that you're lost and use that time for clearing your head.
Just remember that plans can change. If you don't have one at the very moment, then make another one that is best for yourself. Don't rush into anything. Find who you are and what you are meant to do. Find another trail in your life if the one you were currently on disappeared.