Yes, you can receive accommodations in college even if you did not have an IEP in grade school. Colleges do not use the term IEP they usually refer to it as a 504 Accommodation Plan or Accommodation Plan. This is because the law for IEPs does not carry over to colleges. The Americans with Disabilities Act (and its amendments) covers college age students. It says that people with disabilities can not be discriminated against and that reasonable accommodations must be provided by colleges and employers.
Each college has a set of procedures you must follow for receiving accommodations. Check with your college for the specific requirements. Most colleges want you to submit comprehensive testing from a psychologist that documents the disorder. Many colleges also accept documentation from psychiatrists and medical doctors.