What are the reasons why I get infections in my vaginal area so easily? A doctor tld my husband he has too much keratin in his sperm. Is that true?

Depends. Never heard the keratin response. You first need to determine what type of infection--this can be done by your health care provider. If yeast, is he circumcised? If BV (very common) talk about prevention techniques. If sexually transmitted disease--frank discussion with your partner and treatment of all partners.
Sounds far-fetched. Keratin is a protein in our bodies that is deposited in the hair, skin and nails. The sperm propelling tail is reported to have keratin-containing outer dense fibers and a fibrous sheath. That doesn't sound like anything that would preclude you to infections though.