Let me speak straight how this sounds to me. You’re getting some stuff off your chest, because you aren’t happy with how things are going right now - and the course you plotted is seeming to take longer than you had anticipated.
Now you know how capable you are, so just make yourself up a plan and figure how to get this thing done. Cop any attitude about this being just school. Whatever it is, it is the job you have to do right now, and for the next several months. Put the effort into getting whatever extra credit you can, and tactically minimize any damage you are going to take. And figure out what you will do over the summer and fall to make up for any hit your GPA takes this semester.
Something is not working the way you are presently going at it, so see what can be changed. Sometimes change is all that is needed to get out of a rut. Just because the same thing worked up to this point doesn’t mean it will stay golden forever.
It IS tough, but you can do it. And you know it is worth it - the right thing to do. So quit whining and get to work!