ahh yes the old paracetamol and booze combo is not so good.
Basically, you have taken twice the maximum recommended dose of paracetemol ( 4000mg, or 8 tabs ) so that in of itself is not a cool idea. For a healthy young person, taking 8 tabs a day wont hurt you in the short run, provided its sensibly done, ie not every day. Taking 8000mg in one day, or in your case at the same time is certainly a risky move.
One time many moons back, i went out on the piss after having consumed maybe 6 or 8 of the panadeine type pills over a few hours. Sweet jesus was I in bad shape later that night. I had major stomach cramps, vomited heaps and generally felt fucked. I was so concerned that I went to the doc and asked about a blood test cos I thought I may have drunk a spiked drink. Anyway, it was later on that I learnt about the danger of alcohol and paracetemol. I should also point out that i had been taking these pain tabs regularly prior to this event but always within the guidelines.
So as other folks have said, its almost certainly that combo that has fucked you, and seeing a doc would be highly advisable, even if just for your peace of mind. You don;t need to tell him/her that you took 16 tabs, or what your motive was, just say you had a number of them and didnt know that alcohol was a bad idea in conjunction with them.
Try to drink plenty of water, not just now but always as it will assist liver and kidney function. Maybe a liver tonic wouldnt go astray either. Cold water extraction is a fun and easy thing to do but even so I wouldnt get on the piss after youve just swigged down some extracted codeine liquid.
Hope you get better.