Thanks so much everyone for your replies and support

Well i dropped Ethan off at day care today and i talked to the staff about my concerns with Ethan's behaviour. Well it seems they all noticed it too. Apparently last week he gathered up a handful of rocks and then lined them up, he'd then run around around the rocks, mess them up and then do it all again. One of the staff wanted to see what he'd do if she took the rocks away so she picked them up and apparently he got pretty upset. She gave them back and then he started the whole thing again.
There were other things they noticed too, they noticed he was great with his fine motor skills but awkward and 'floppy' with his gross motor. They didn't want to tell me because they wanted to wait a few weeks and see if it improved but since i brought it up they were keen to talk about it.
In a way i'm glad they noticed these things so now i know i'm not just being paranoid but at the same time i'm so sad because now i know that there is a big possiblility he has ASD. I know he's still the same little boy and i don't want to jump the gun and diagnose him without even seeing the doctor but i just know, i just know in my heart thats what it it. I guess i've known for 2 years really.
So i asked the staff to watch him today and let me know if they've noticed anything when i pick him up at 12:30pm. I'm really nervous for him today because its raining here so he can't go outside to play which means he'll be stuck inside with 29 kids and i don't know how he'll cope. When he was younger he used to get overwhelmed with a lot of people around. I asked the satff to call me if he gets upset and i'll pick him up early.

Anyway so i'm looking forward to his doctors appointment on Monday. I know the doctor can't diagnose him straight off but i'm at the point now where i just want to have an answer so i can educate myself to understand his needs and wants better.

I feel like i've been blind to things he does that are obvious traits of ASD. I remember reading signs and symptoms of ASD on the net and thinking 'hmmm Ethie doesn't do that, or that' but now that i've been watching him more closely i realise he has a lot of traits. These are the things i've noticed

*Obsessions that dominate his speech and play
*echolalia
*repetive speech patterns- repeats the same thing over and over (usually about his obsession with plugs and sinks)
*repeditive body movements- he'll jump twice on the spot when i repeat whatever he's saying back to him...only picked this one up a few days ago.
*Runs with his head to the side sometimes
*lines things up
*flaps his arms occassionally
*strange fears
*fixated on unusual parts of things. For example he loves Hi 5, one of the episodes had the gang pretending to be cows in a paddock and the sun was shining in the sky. Now everytime he sees or talks about Hi 5 he says 'mooooo yellow sun' over and over even if he's watching a different episode. He'll also say it at random times.

So thats where we're at. Thank you all so much for taking the time to comment and offer advice. Its nice to know i'm not alone in this.

* forgot to mention, Ethan is 3 in August*