Child dentist

Are there any child dentist that can advise me on the best toothpaste for 2 year old who has stains on bottom teeth. I consistently brush his teeth twice a day for as long as he can stand (absolutely hates it I have to pin him down at times). I’m getting really upset for him as I feel I should have done more? They’re not overly obvious to anyone but me at this point but I don’t want to let them get worse before I can get in with my dentist in April. Any toddler safe product recommendations will be appreciated. Thank you!