should i be worried

COBs are very competitive and unlikely that many will do them. I am assuming you'll end up rushing next year. Don't worry about finding your place, you still will and you'll still have an amazing time. A lot of people feel similarly to you, its going to be ok.

First off: don't worry!! You'll find your place here, whether that's in a sorority or not.
A huge number of girls end up dropping from rush, it's a lot more common than is advertised. As someone on the other side, don't take it too personally. It's all a numbers game and factors like connections to girls in the chapter, legacies, etc. can let some great girls fall through the cracks.
If you're still determined to join a sorority then hope for a COB. A bunch of houses do them even if they hit quota (they just want to grow their number beyond quota). If you want to take matters into your own hands, reach out to any sister or new member at the houses that you had left in the later rounds of rush and express some interest in a COB.
If that doesn't work out, there's still informal and lots of great houses do that too. Last year I believe SK, AXO, Tri Sig, Zeta, SDT, and Gamma Phi did it (I'm not positive about these though).

If you have any friends who got into one of the houses you loved, let them know you're interested in COB. Some houses do it on the down low so don't be shy.

Agree with the others, COB's are very possible. Just because a sorority hands out COB's doesn't mean that sorority is any lesser than the ones that don't