I can't wait until mid-May.

I applied as a transfer also. Unfortunately I don’t have the luxury of waiting until mid-May and I have to respond to my other offers by this weekend.
I have been on edge all week and I don’t know what to do. I really want to go to JHU.

Can you accept your second choice and then tell them you changed your mind? You’d lose your deposit, but I don’t think there are any other ramifications.

^ that makes the most sense.
You could try calling the other school and asking for some kind of extension, but I wouldn’t get my hopes up on that route.