I gave birth to my second child 13 days ago and 5 days ago I began to have severe abdominal pains and diarrhea. Infection?

Could be. Please see your doctor and have an abdominal exam. If you've just been in the hospital or had antibiotics recently, you're at risk for a certain infection called c. Diff that can cause cramping and diarrhea. Severe abdominal pain should be taken seriously. Please see your doc.