Most likely the beer has been kept too cold since bottling. The beer should be held for a week or so at a temperature of at least 55oF. Move it to a warmer place. Another problem may be that you didn’t use enough (or any) priming sugar. The usual amount is 1/2 to 3/4 cup in 5 gallons. Your caps may also be leaking. This happens when you use “twist-off” bottles or when you boil the caps to sterilize them. Boiling can destroy the integrity of the cap’s seal. Sanitize with iodophor (properly diluted). If you use bleach, a chlorine odor can be retained by the cap liner, and this will affect your beer’s flavor. It may also be that you left too much sanitizer in the bottles. Let the bottles air dry upside down before bottling.