I am a university student, doing a scientific bachelor study. I plagiarised multiple exercises from multiple homework sets for three different classes, all in all about 50% of all the homework for those three classes. I passed the final exams of those three classes. Realizing what I have done, I am considering turning myself in, unless the punishment would be too severe. What do you think?

Edit: I actually got caught once before for plagiarising on a single homework set.