you'll be safe. run the full course. avoid long-term antibiotic use because it will inhibit your body's protein synthesis. eat yoghurt only if you like it.
details below.
this depends on the type of antibiotic. most antibiotics work via inhibition of some aspect of bacterial protein synthesis. the particular step they inhibit depends on the individual/class of drug and determines how effective it is against which bacteria. azithromycin kicks gram-negative ass but has very wide action.
trick is, human cells also synthesize protein. tetracyclines have pretty serious systemic effects and are not prescribed to children often for this reason.
as far as yoghurt helping? i can't imagine why it would, honestly. it has nothing to do with your digestive tract.
there are a few things regarding azithromax that are relevant to bb. it inhibits cyp3a4 production, causing all hormones to be broken down slower in the body. however, erythromycin, which belongs to the same class of antibiotic, is well-known to fuck up mitochondria. that's bad for energy, growth, metabolism, everything. it's also an anti-inflammatory, which is generally associated with less growth.