Hello - I can definitely relate to this - there's a wonderful connection between having children and dental issues. In a situation like this, you have to weigh the benefits vs the risks. It sounds like you've got an infection, and trust me, you cant afford to put it off while pregnant. Or, you'll end up like me, needing an implant but wont be able to get one (maybe a bridge), and it all started with a cavity. Maybe they can try giving u a round of antibiotics, but it sounds like they're gonna have to go in there and clear it out. A root canal isn't that bad - the worst part, in my opinion, is having the needle stuck in the roof of your mouth or in the gums to get the novacaine in (and if you can survive labor pains...) anyway I just had one last week, actually...and had my 2nd child 3 months ago. The filling was done a year ago and it just started hurting in the past few months - turns out it was deep enough that the filling only worked for a little while. They might need to take a few more X-rays but if you're double shielded u should be fine. Heck, I didn't know I was pregnant with my 2nd child til I was 14 wks along and had Xrays and dental work done at 10 or 11 weeks. I was upset at first when i realized this, but nothing i can do about it now, and my boy is fine. Anyway, with the root canal I just had, they had me take antibiotics just to be safe. I didnt want to tho cuz I nurse my son. But I had to...and dealt with a few really messy diapers and colicky nights...i took all but 4 of them(cuz I felt bad for my son!)...Now I need crowns but lost my job (the place I worked at closed while I was out on maternity leave - !) so I have to wait til I get medicaid to do anything...
anyway, discuss your options with your dentist and OB, even your primary. They'll probably tell u the same thing. Teeth take a toll when we have kids - so definitely up your calcium intake (at least 1,200 mg/day). Keep in mind too that Iron inhibits Calcium absorption, so don't take calcium with your prenatal.
Hope this helps and good luck!