My Anxious Four Year Old

I just recently finished the book "Stuff" which talks about hoarding. The last chapter deals with children who cannot bear to throw anything away; when their parents forcibly clean their areas it causes major trauma. I'm not suggesting your son has this (there was talk that hoarding may be a component of OCD) but in each of the cases their hoarding or obsessing about objects started somewhere. The families addressed their children's problems in different ways: medicine, therapy, etc. They all learned to live with their child's tendencies even if those obsessions isolated them eventually.
Stress manifests in many ways and this issue may resolve itself once he understands that he is not going to be abandoned. He has no control over you leaving him but he CAN control picking up these miniscule objects. It sounds like a fixation to me, one that I would pay close attention to.
I hope you are able to help him with this and get to the bottom of why he's picking up things. I dare say that's not the real problem...

K.

Does he get punished at daycare for not picking things up after himself? or anywhere really?... just kinda sent up a red flag to me. BUT a couple days ago I watched a video of a dad who set up a nanny cam cuz his son listened to this lady (his mom's roommate, grandma's roommate) extra good and would get anxious if the remote control wasn't on the table and it was because she was beating him when he didn't listen and when SHE couldn't find the remote... so that's probably why I'm being paranoid :)

Since he is older try to strike up a casual conversation randomly and see if he will tell ya why he is so anxious about things on the floor.

Ask your pedi- sounds like OCD to me, but, honestly, I'm not a professional.
Ask your pedi if counseling would be beneficial for him to learn some coping mechanisms for the anxiety. Anxiety is a horrible thing to live with (I had panic disorder back in college. Went to a therapist who specialized in anxiety issues, and have been panic-free for close to 20 years). I found some articles that might be helpful:

http://www.livestrong.com/article/13388-identify-symptoms...

http://blogs.psychcentral.com/anxiety/2009/05/more-about-...

Time to call your pedi and ask about getting some help with his anxiety. Your pedi might set you up with a counselor, or maybe a panel of people who could evaluate him for OCD, anxiety, sensory issues, etc. But please do reach out to the professionals... this one is too big to deal with alone, because untreated anxiety can lead to lots of stress for your son (and you). With the support of experienced people who know how to guide you with this, you'll learn how to help your son quickly. Good luck!