Don’t spook yourself. No matter what it looks like, NONE of them have made “solid” friends in 3 weeks. They may be off to a quick start, or they may turn out to be foxhole buddies that will change in another 3 weeks or 3 months (the most common times for early friend groups to re-constitute themselves is around 6 weeks and 3-4 months). But nobody makes solid friends that fast. It takes time - and some good and bad shared experiences- for people with whom you are friendly to turn into real friends.
100% you are not the only person at your college or of your friends to be feeling this way. Take a deep breath and go back to basics: focus on things you really like to do and really need to do.
For the things you really like to do, find other people who like to do that as well (clubs, activities, etc). For the things you really have to do (whether it’s study for a test or doing laundry or going to the Admin building to sort something out) look for other people who have to do the same thing. A specific, time limited, shared activity is a low-barrier way to get started knowing people.
tl;dr: completely, 100% normal!