If one has virul infection and takes antibiotics, will it cause any severe side effects? ie; on stomach greater then if one has a bacterial infection

Not indicated: Antibiotics should not be used for viral infections. Antibiotics can have negative GI side effects.

See below: You should not take an anti-bacterial antibiotic for a viral infection. It will be of no benefit. All antibiotics have potential side effects and toxicities that are the same whether taken during a viral or bacterial infection.