I often get throat infections. sometimes so severe that i need antibiotics. what can be the causes?

Viruses/bacteria: Often tonsillopharyngitis is viral from a cold and then, if prolonged, or your immune system is overwhelmed, it becomes a bacterial infection requiring antibiotics. There are many bacteria besides streptococcus that cause throat infections. Sometimes, your tonsils will harbor resistent bacteria that reactivate and cause problems when you catch a virus. See an ENT to discuss this and examine you.