I'm not a Dr, but I play one on the internet sometimes just to mess with people

As Christine has pointed out, biopsies are really not a big deal and I would insist upon it if only for peace of mind. Being pregnant undue stress and worry isn't good for you or your baby, that being said, you've gone to 2 different Oral Surgeons who've told you it's nothing. If you are still not satisfied (and apparently you are not) then insist upon a biopsy.
I will say this, my wife was very "sensitive" while pregnant with both of our boys, while I encourage precaution I also think it could be emotions due to hormones. Remember that these medical professionals can be held liable if they miss something like cancer and you've had two "oral surgeons" check you out and dismiss it. It could be a number of things going on in your mouth and not necessarily cancer, keep an eye on it but really don't let it stress you out. If you can't get your head wrapped around it, get an appointment with an Ear Nose and Throat surgeon.
Keep your chin up!
Eric