Need good excuse for skipping class?

I just started university about 2 months ago. I never attend the lectures or tutorials. Rather I just watch the recorded lectures and do the tutorial work at home. This works for me and I have been getting good grades. Lectures and tutorials aren't compulsory at my university... for like 95% of courses. But I just found out today that one of my courses has compulsory attendance. I sort of just assumed that it didn't, which was stupid. Anyway, my professor sent me an email asking me why I haven't been to class and saying that attendance is 10% of my grade. I'm going to start attending that tutorial but I don't have an excuse to make up for missing the first 8 tutorials. I don't know what to say. Should I say that I had other commitments or maybe personal issues? Or should I say exactly what I said here even if it will make me look very stupid?