With only 1900 miles it should be fine. That does not mean it is. If it is not humid and it is warm it may be something else. When you say the exhaust smells normal, there is no scent of burning oil? I mean are we talking a wisp of white smoke, or good amount, or are mosquitos falling out the sky?
Is your aircleaner clean? No mouse nests no leaves? Was it over oiled? How are your plugs? You can tell alot about a engine, by warming it up driving gentle, drive it semi aggresivley, then keep the revs up coming home, while still keeping revs up turn it off and coast into your work area, quickly (I know its hot but it can be dealt with) remove and check the plugs against a plug chart. Champion has one if you look with google.
You will probley not need to do this, it may just be the aircleaner being over oiled. It might of been overfilled with oil, and the system is sucking the extra that gets slung around up into the air box, soaking your air filter and burning it that way.
If the intake system is normal and you are sure, if the oil level is correct and you are sure, the next step is in my mind a vacum test and compression test.
Parts do fail, the more of them you make the more that are out there to have all the odds line up and fail.
Dont freak out! Start with the simple stuff. 99% of the time its the simple stuff.
Just my take on the matter and how I would handle it, based on the discription you provided.
Steve