Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain white coating over the tongue is an indication of oral yeast infection known as Oral Thrush and as during Pregnancy the immunity of the pregnany woman is also and also hormonal changes can led to increased chances of fungal infection.. Nausea and vomiting occurs due to high levels of pregnancy hormones leading to nausea.. Yellow coating is not due to any infection and is commonly due to accumulation of food debris over the tongue along with some levels of bacterial overgrowth.. Yellow coating is generally not an indication of anything serious.. I would however suggest you to consult your Gynaecologist and get evaluated and a thorough clinical examination and investigations like Microscopic examination of the scraping from the tongue can help in diagnosis.. You can be advised to take Vitamin B complex supplements, lemon juice,a balanced diet and avoiding stress for reducing nausea.. You should also drink appropriate quantity of water.. Take sufficient rest but do not make yourself sedantary. For tongue coating use a tongue scraper to clean the tongue.. Use a soft toothbrush to clean your tongue.. Do warm saline gargles. Chew raw fruits and vegetables as they tend to clean the tongue by frictional action.. Limit intake of tea, coffee and carbonated drinks.. In case of thrush you can be advised to gargle with Nystatin mouthwash, but take precaution not to swallow it.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.