Just wanted to say-the big difference between checking yourself/having sex and a doctor checking you is the type of bacteria. The flora on your (washed) hands and on your husbands penis is something your body is accustomed to. The chances of it making you sick are very very small. Also concider that a penis doesn't enter your cervix at all, whereas during a cervical check they may be sticking their fingers IN the cervix.
The flora on a doctors hands, the gloves he wears, etc are not the same as what you find in your own home. In fact, some of the germs at a doctors office or hospital are downright scary. Even so, its just the general germs we aren't accustomed to that can cause an infection. Yes, they wash their hands (hopefully!) and they put on gloves but as someone else said, those aren't sterile gloves and they aren't usually terribly cautious while putting them on, so you still end up with all sorts of non-normal flora being pushed into your cervix.
Btw, even a papertowel has an insane amount of germs on it-we did stuff in microbiology where we prepared plates before and after washing our hands. My after looked worse than the before (WAAAAY WORSE!) and at first we couldn't figure out why. Then we realized that I actually dried my hands with a papertowel. We checked this theory again by preparing new plates and sure enough...my hands seemed cleaner BEFORE washing and drying them with a papertowel! (they were very much cleaner after washing and letting them air dry though)