I personally wouldn't say that your cyles are irregular, since they are 31-39 days long, seeing as a normal cycle is anywhere from 26-35 days or so. Usually an irregular cycle is when you either do not have a period for a couple months on your own or you have to take something to induce your period to show. But if your doctor considers you to having irregular periods then disregard what I mentioned.
I normally only have a 3-5 day period. It can last up to 6 days if I spot more than usual, so I wouldn't think that your 2-4 days is unusual.
Adult acne is one of the symptoms of PCOS, but doesn't necessarily mean you have PCOS. Not all women get acne, and not all women with acne have PCOS.
Because you are getting your period on your own (I'm guessing about this since you didn't mention anything about taking anything to bring it on), then I would say that you are ovulating on your own. This alone would make me think that you don't have PCOS or if you do that it is a very mild case of it and that it's probably not the main cause of you not consieving. Now again, this isn't always true, only what I've read and heard from other ladies on here.
As far as I know, you cannot be diagnosed with PCOS from a PAP. Normally you are diagnosed from an ultrasound of your ovaries or from a series of bloodwork. The main thing the doctor will look for in the ultrasound is if you have a string of pearls on your ovaries, again not all women have this but can be diagnosed with PCOS. As for the bloodwork, there are many tests (can't remember which all they are since you go through a series of like 8 different tests). Depending on the ratios of these results the doctor may diagnose you with PCOS.
If you feel you may have PCOS and your doctor does not do any tests, you may want to consult another doctor for a second opinion. Since 10% of the female population has PCOS and I think about 1/2 of them don't know they have it, it's something you may want to look into to see if you have it. There are still a lot of doctors out there that do not know enough about it to diagnose it, but there are many who have spend a lot of time researching it and can help.
The major symptoms of PCOS are the string of pearls on your ovaries, adult acne, high testosterone level, being overweight (although not all are), irregular periods (usually 6 or less a year) and other things. There are some great links on the welcome message
WELCOME MESSAGE and GREAT PCOS INFO LINKS! that can help you out with more questions and lots of reading. There are also a lot of books out there regarding PCOS that can help you answer some other questions you may end up having.
Good

Luck and let us know if you have more questions.