I am quite astounded by this thread. First, @PeterEmrys , relax – you are getting a degree from one of the top universities in the world – you are not only fine you are way better than fine. You are accomplishing a great thing, and studying something you have passion for.
Most young people your age don’t know what they want to do. And most careers don’t have pre-professional undergrad degrees; so you have DONE NOTHING WRONG OR BAD. In fact, you are like most of your peers.
Get your degree, figure out what you want to do, and then pursue it. Grad school, law school, MBAs will be there when you decide.
Stop looking for people to tell you something like “I have one word for you - plastics”. That was a joke when The Graduate came out and it is a joke now.
Get some entry level jobs, maybe travel, explore options as you can afford to. Just relax. If you were smart enough to get into UPenn you are likely to figure it out. These things usually work themselves out also. Your future is bright!