Annoyed thatI wrote you a long reply & lost all of it due to damned road works affecting my IC 
Try not to feel so bad, I was in your shoes with Dd at 2.5 months - on my birthday - I felt like the worst Mum in the world as Dd was having a tooth out under GA
- even though up to then she'd NEVER eaten sweets, chocolate or had any other sugary nasties , such as ketch up, squash etc etc
- the dental hospital DIDN"T criticise - I did ask though as I was so confused by it, friends 3 DCs ate sweets & drank squash daily & yet had NEVER had any dental trouble 
Dentist suggested it might be milk, but did say that some DCs just have weaker teeth - mine certainly has, as by 8 she's had 2 teeth taken out & 2 fillings - yet still rarely gets sweets etc, due to allergies & us being health food freaks & cleans her teeth properly at least twice a day 
An alternative therapist friend reckons theres a connection between stress in pregnancy & DCs tooth enamel being weaker - certainly fits for us & another friend whose elder DC had the same problem - she had a special coating painted onto the adult teeth, something I intend to have done with DD at a later date.
Hope that helps & DD recovered really quickly & wasn't in the least bit stressed or in pain :) - & my DD is a real little worry wort, so yours will no doubt be fine - just try to keep yourself calm so as not to pass on your own fear to DD - oh & Lavender or roman chamomile aromatherapy oil on ther clothing can help with that 