Thank you for your question about your camellia plants.   Here is a link to a rather basic article about the care and feeding of camellias.  As for your problem, I think there are 3 things going on.  First is that camellias need consistent watering, especially after they set buds. (I'm assuming from your question that the plants aren't setting buds, as opposed to dropping them after set but before bloom.)  Last summer and early fall were very hot and dry, and these shrubs need water so they don't get stressed just when they need all the help they can get to produce buds.

Second, I'm wondering if you've tested your soil to make sure that your shrubs have enough nutrients (since you didn't say anything about your fertilization schedule.)  You might want to consider submitting a soil sample to a testing group, such as A & L Western Labs to see whether the soil is deficient in either phosphorus or potassium.  (The lush green in your plants' leaves would indicate there's enough nitrogen, but you won't know until you get an assessment and recommendations for nutrient supplement and pH modifications, if necessary.)

Last, your concerns about not pruning may be unwarranted, and a good pruning may even restore blooming potential.  Pruning helps invigorate the plant, and may allow more sunlight to reach all the leaves.  If shrubs are crowded, the higher leaves shield light from the lower leaves, and sunlight is essential to blooming.  Here is a link to an article from the American Camellia Society that explains.  However, pruning at the right time is also essential.  Since buds set on last year's growth, pruning in summer or early fall will remove what buds were there.

I hope this information proves helpful to you.  Good luck!

 Thank you for your information. I have now pruned back the Camellias and found all kinds of buds which have not opened yet, which is kind of late for these types of bushes.  However, I found little black bugs (?) on the buds. See photos. What are they and how do I get rid of them? Are they preventing the buds from opening?
Thank you for your response.

Thanks for these pictures.  Your plants' buds appear to be infested with aphids, which normally occur later in the year.  Aphids have a variety of colors, ranging from white to yellow to red and black.  They are sucking insects, so, with a 'healthy' population, can such the sugars out of the softest tissue on the plant: the bud.  I can find no references to aphids on camellias in Oregon, although The American Camellia Society has this page on them.  Although you can attempt to eradicate them with a strong stream of water, you can also use an insecticidal soap, described here.  Insecticidal oils, such as neem oil, are also effective if they land on the insect.  (The oil essentially asphyxiates them.)  However, once it dries or is washed off, it is no longer effective.  (The good news is that because oils and soaps aren't systemic--going into every cell of the plant--they are not harmful to beneficial insects.)

Because these insects are so prolific, you will need to keep seeking them out and treating them.  The other thing you might see is an influx of ants, since the nectar produced by the aphids is tasty for the ants!  I hope this is helpful, and that you get more blooms in the future!  Good luck!