Ur baby is prone to infection since birth... Had infection after birth..As u said. mineral water or purified water ..? most of the bottled water is  purified water and not mineral water... Feeding baby with plastic bottles should not be a concern practically...as most of the babies are fed using plastic bottles Yes,  baby not breastfed.. That is a concern because mothers milk is complete food for baby and protect  baby from diseases( improve immunity) Antibiotics use sometimes become essential to control infection... Don't worry.. Take ur child to a paediatrician... He will examine child and assess his milestones  and will do what is necessary...