Consult your doctor as soon as you suspect your child has a learning disability. It can't hurt to test for one, even if your suspicion is wrong. The longer you go without knowing what the problem is, the more frustrated your child will become with the learning process.
Contact special education teachers at your local schools. They may know about local resources or learning disability experts nearby who can guide you. Consider getting a copy of "Complete Learning Disabilities Handbook," second edition, by Joan Harwell. It's for special education teachers but can give you some ideas about teaching your child.
Search Google for "homeschool learning disability" to get a list of online resources. Join the LearningAbledKids discussion group on Yahoo! to connect with other parents who homeschool. The LearningAbledKids website has lots of information about learning disabilities.
Acquire the book "Learning disabilities: A to Z" by Corinne Smith and Lisa Strick. Rated five stars on Amazon.com, it's a guide for parents and will help you throughout your child's education. The Learning Disabilities Association of America (LDA), which was started by a group of parents in the '60s, advocates for people with learning disabilities.