Hi L.,
My daughter, who is now 9, was diagnosed with SPD when she was 5 (she'd been going to speech since she was 3 through the school district, and they did testing and she qualified for OT/PT, but it wasn't until she started Kindergarten that we figured out what she had. I diagnosed, and her Childhood Specialist confirmed).
For my daughter when she was younger, it was loud noises, loud music, bright lights, being overstimulated, or not being stimulated enough. Itchy/scratchy fabric, too tight clothes, anything that buttons/zips at the waist (we use elastic waist pants). She will be in the 4th grade in the fall and still has trouble with telling time/conceptualizing time. She also struggles with transitions and making a decision (can't push her for a fast decision; throws her into a tizzie), and social issues as well. And on top of the SPD, she is also a highly sensitive child. Yeah. She's like a young adult in a child's body. She has a hard time understanding why kids do what they do and why they don't listen and why they're mean to other kids and why everyone can't be nice. So those are issues we work on every day.
She's very emphatetic, and very smart. She also suffers from low self-esteem, which we continously work on. She wants to be perfect, and we have to work on the concept that one doesn't need to be perfect.
I have answered many, many mothers' questions about this one, so you'll find quite a bit of information if you read through my previous posts; I also have listed some books that I found highly helpful in dealing with my daughter. If you don't find the list of books and are interested, please contact me and I'll send the names of the books I have on my shelf.
It takes a lot of work (and it's continuous work), but every year, my daughter is able to "live" in the world better and better, and her ability to form friendships and "relate" also gets better. We have her in speech and OT/PT in the school district, and she also sees an outside OT/PT person for more specific specialized help, as well as still seeing the childhood specialist/psychiatrist. We've found that taking her to see a psychiatrist has been an absolute lifesaver for our family, as the older she gets, the more issues she has that she doesn't necessarily want to talk about with us. And my husband and I find that we really don't have any good ideas to give her for dealing with her unique situation(s), so we love her specialist. And as an added bonus, I also get some "mom help" and ideas on what my husband and I can do to help our daughter. So we've found our daughter's specialist to be a real family saver. Plus, it helps that we love her as a person and think the world of her (our daughter first saw her when she was a Post-Doc student, before she became "professional," and that might also have something to do with how well we all get along. She's also one of only a handful of child psychiatrists in the country. We live in Madison, WI; if interested, let me know and I can tell you who we see.).
It's more extra work, but I'm so proud of how well my daughter is doing. Yes, we still have to deal with the "flight" response once in a while, and with being overscared with certain things/issues (like having to have a scab scraped off by the dr after having a wart burned out, or going ballistic and terrified when we just dealt with head lice), but those huge blow ups or issues are getting better to deal with and the blow ups lesser as the years go by.
The key is having as much help and as much knowledge as you can get so that you can help your son with his own unique needs and challenges.
Good luck. And if you need someone to talk to, or you have specific questions, please, contact me. I've done a ton of research and reading on the subject, as I'm sure all the moms with SPD children have. You're not alone.