to the Forum!
It definitely does sound. like an anal fissure. Sometimes, like any small cut, as in one on the edge of the mouth, they can be difficult for a doctor to see. They are also quite common after having a baby. You would be better to see a Colon and Rectal surgeon about this rather than an ordinary doctor, if you have not already done so. They are far more used to these sorts of things. The burning sensation is common and a clear sign usually. Personally, if you need to have them take a look, say that you only want a sigmoidoscopy, unless anyone in your family has had problems in the area previous to you.
Do make sure that you are drinking enough water with your breastfeeding, and
don't increase your fiber unless you eat less than 25g a day of it. That will just make your BMs more difficult to pass. Take something like Miralax or Milk of Magnesia. I found stool softeners to be useless. Miralax is what is recommened.
Also, invest in a Sitz Bath and sit on it and bathe your rear end after (and before if necessary) a BM.
Most important of all, you are still in the chronic stage of an AF, a time that if one of these doctors were to prescribe (if you can have these while breastfeeding) one of these ointments/creams, you have a good chance of healing. Suggest Diltiazem, Nifedipine or Rectiv (can give headaches the last one) to the doctor you see most.
Also, have a look at the posts and information on here under the sub-forum for anal fissures. You will find lots of information there.
Feel free to rant! We know what it is like, believe me.