I think whenever you feel like your concerns are not being addressed it's time to switch pediatricians. She should at least give you reasons why she's not concerned. I think it's fine for a doctor to disagree with a parent about parent concerns, but they need to give you reasons. It irks me when I feel brushed off with no explanations given, or dumbed down explanations, as if I'm too stupid to understand.
Also, make sure you give HER reasons why you think it could be ASD or OCD, for instance a checklist, and name the characteristics where you have concerns. Otherwise there is no way for the doctors to determine which parents are fruitcakes and which have done actual research.
Seconding blackcat's advice.
FWIW, I also have some questions - these aren't meant to pick apart your concerns, but might help you look at this from the ped's perspective. The ped, also, has actually seen your child - which is something none of us here have had an opportunity to do. Anyway, I'm not clear from your post if you're concerned that OCD/ASD might be present, or if you want to rule it out. Also not entirely clear if you're wanting confirmation of giftedness and are concerned that you need to be addressing the potential gifted abilities. One thing that is confusing to me is - how is your 18-month old able to put his dishes in the sink and turn off lights? Please note, I'm not questioning that he's doing this, but my limited experience with 18-month olds, light switches and sinks makes me question it because of height. Is it possible your ped is hearing things that just don't make sense to the ped from the normal realm of childhood and therefore discounted not only those things, but other things you brought up? Also think about how you presented what you were talking about - if you're seeking a referral make it up front, clear, direct, and have reasons to support it.
We've had issues with a ped and early childhood drs in our family in one specific instance with a child who had medical issues that didn't fit the norm of what the drs were used to seeing. Two big roadblocks that were difficult were: 1) dr's ego - drs who felt they were being questioned when we weren't able to report back what they expected to hear, and 2) limited time during an office visit - our dd's drs were heavily booked and didn't expect to have to spend more than a few minutes with each patient, and became annoyed when we had more than a few minutes worth of questions that weren't easily answered.
Another issue we ran into (same dd) were drs who made assumptions based on behaviors/etc they saw within the limited timeframe of an office visit - which is an environment that the child isn't usually living in, hence isn't exactly the best illustration of "typical" behavior for the child. It sounds like there's a possibility that in your situation the dr is seeing a child with no behavior issues partly because they are observing in a limited window... a work-around for refocusing on true issues is to have a list with you that you've put together before the appointment, listing what you see as concerning behaviors.
My advice is to take a step back, clearly define in your own mind what it is you're seeking, find supporting evidence, and try again with a new dr. Think through the roadblocks you might encounter at that dr visit and be prepared with a plan if they pop up - for instance, if the dr seems to be short on time, let them know you have more questions and ask if you can leave a list and have them call back or schedule a follow-up visit, or ask what you can do to get your questions answered. etc.
The other thing to do: filter your list to only include pieces of data/info that fit with what you are concerned about or make sense in the story you are trying to convey. For instance, in your OP you mention toilet training, the dr said don't worry about it until your ds is 3, you're noticing signs of readiness. In reading the post, it's not clear to me how this relates to what your concerns are - I hear the dr saying that not being ready to toilet train isn't an issue until 3 (which mirrors everything I heard as a parent of young toddlers), and I also hear you saying you see signs of readiness so you're frustrated that the dr is mentioning don't worry about it yet... but I don't understand how any of this applies to your concerns you're trying to follow up on with the dr re ASD/OCD - which is, I think, your priority concern. I realize this sounds like I'm picking your OP to pieces, and really I'm not - just trying to make a point, when you have very limited time with a dr, you'll want to be as clear as possible and not get off-focus with extra questions/etc.
Hope this makes sense!
Best wishes,
polarbear
ps - this is just a total guess, but I'm wondering if part of the reluctance to finish off the 18-month check at the 17-month visit was vaccine schedules - there are several boosters/vax required in our state at 18 months which can't be given sooner.
