As you're stating that the doctor did some 'enamel coating', there is high possibility that the composite or other coating that was placed does not have properly finished or smooth margins. This, if true, can cause food accumulation leading to gum infection and bleeding. A clinical examination is necessary to evaluate your actual problem. Treatment could be Cleaning, Smoothening of irregular margins if any, or replacement of the earlier 'enamel coating' with a cosmetic veneer or crown.

First stage would be a Thorough scaling .Once its done go for Asthetic/cosmetic treatment of discoloured teeth Regards Dr. Ratnika Agrawal, Smile Up Dental Care & Implant Center of Kharadi in Pune

Bleeding gum and yellowing of teeth are two different problem Veneering will be excellent choice on your case 

You might required proper scaling followed by cosmetic treatment of discoloured teeth.may be simple bleaching will serve the purpose

It means u have two separate problems. Yellow spots r due to dental fluorosis which r internal stains. They can b covered with laminates or crowns. Bleeding & smell r due to plaque and calculus which can b removed by simple cleaning.

Bleeding gums could be due to Gingivitis(inflammation of the gums)due to improper oral hygiene and irregular professional cleaning.Get your regular cleaning of the teeth and check ups done at regular 6 month intervals to keep your gums and teeth clean and to get rid of of odour causing bacteria.Use zinc containing mouth washes and consume plenty of fresh fruits and vegetables to keep your oral tissues healthy. The yellow stains,if extrinsic(external) can be removed with bleaching procedures and if it is intrinsic(deep seated) you can opt for cosmetic procedures like Veneers or Lumineers. Regards

Hi.. undergo Laminates or zirconia crowns for permanent solution. Regards

Please post pics . go for scaling for bleeding gums and for esthetics u can opt for veeners