Seriously people! There are safety instructions on the packets for a very good reason! Paracetamol overdose is very serious, it has a narrow therapeutic index, meaning that it doesn't take much more than the standard dose to cause you harm. Don't take more than it says on the back of the packet.
If you're really feeling bad, you can take paracetamol, ibuprofen or aspirin, decongestant (so long as it doesn't also contain paracetamol) and codeine together, but make sure you obey all the recommended doses.