Definitely make sure to floss and maybe use a mouthwash (like listerine). My dentist told me that it's quite common for gums to get a little bothered in pregnancy, which means they recede a bit, so that more of your tooth is exposed at the gum line. You might not notice that it looks any different because it's such a small change, but the receding in the gum would probably expose the sensitive parts of your tooth. Sounds like it's better now, but just take extra good care of your teeth. If you're in the UK and haven't been for awhile, go get a cleaning at the dentist. It's free. I had one done in 1st tri and my teeth felt a lot cleaner after and I've had no gum/sensitivity issues (though I've had them in the past, when not pregnant).