Generally, every level of math gets more difficult and/or students learn new things that might require them to put in more effort than they did before. That’s all normal/to be expected.
You’ve received good advice and using IXL and Khan to study and also talking to your teacher all make sense. There is nothing to fear in talking with your teacher, they are there to help!
If you do end up with a B in this class, or any other, that would not (generally) signify that one was really struggling in a class. In the future there will likely be classes where you have to work really hard to get a B, and will be proud of yourself for that outcome.
Lastly, and I do remember what it’s like to be stressed about grades, but I would encourage you to change your user name simply for the sake of putting positive thoughts out into the world. Maybe simply an opposite word of your current name (confident, optimistic, etc.) or any other set of words/numbers/initials that you might like. Posters want you to stay around here all thru HS, and I bet you may not always want to see ‘anguished’ when you login. We are all rooting for you!