Maydup is right. Antibiotics blitz everything, including all the beneficial bacteria which live in your gut. It would not surprise me that diarrhoea is a consequence of that because, simply through sheer number, they usually out-compete the kinds of harmful bacteria which give you the trots.
I don't think it is a good idea to take pro-biotic yoghurt with the antibiotic tablet as, in effect, you are using up a chunk of the antibiotic dose to kill off the live bacteria in the yoghurt, leaving a weaker dose to treat the infection elsewhere in your body. (Ask your doctor about that one!)
When you've completed the course of tablets -then- (following day) eat the probiotic yoghurt for a few days to get your gut back to normal.
With regard to the tipple (I liked the phrase 'cooking whiskey', totally new concept to me, lol) the reason that the tablets say 'avoid alcohol' is not because the combination can make you ill, it's because alcohol damages the antibiotic, makes it ineffective and prolongs your illness. (Subtext: you need further doses of pills, costing the NHS more money!)
As jno and boxie have pointed out, all varieties of tablet will cause a bad reaction in a small number of the people who try them. Make sure that this gets recorded in your medical notes.