Mam, Pain In Teeth can be due to various reason, but most commonly because of caries or decay and infection.
During pregnancy first 3-4 months are very risky and no dental Treatment can be done. But after tha from 4-9 months, dental treatment can be done. Only problem is you might feel discomfort for sitting for long time on dental chair.
Next Steps
I would suggest go to dentist and start a root canal treatment, but do ask the doctor to keep your appointment short. You can only take paracetamol pain killer and nothing else