Hi there! Welcome aboard! I'm so sorry to hear about your pain, but it's all too familiar what you're describing. Unfortunately, a proper diagnosis can only be performed by a physician, preferably a colorectal specialist. If you have any family members who might be able to donate to at least one evaluation, it would be a good idea.
If your fissure is new, you are in the best possible phase to get it to heal naturally. Another reason a visit to the doctor would be helpful is a colorectal specialist can prescribe you an ointment to help relax the internal sphincter spasms and assist in healing the fissure. Ointments such as nitroglycerin, nifedipine, or diltiazem.
At home, there is a lot you can do to help your fissure heal. First and foremost you need to make sure your BMs are regular, soft, and that you never strain. If you can accomplish that with diet alone, great. Most people, however, find a stool softener or something like Miralax to be a godsend in keeping the stools soft and easy to pass. With diet you'll have to experiment a lot with levels of fiber to see what woks for you. Keep in mind that too much fiber can actually make stools too bulky and a lot of fissure sufferers find that the constant stretching of the sphincter by bulky stools just keeps re-opening the fissure further. Also, if you do increase fiber you have to increase your water intake to prevent constipation.
It's important to keep the anal area clean, but be careful about the way you clean up after a BM. Never drag dry toilet paper across the anal area. Use moistened tissue and blot gently. Following up with either a hand held shower or a warm bath can help both with cleansing and with pain relief as the warm water will help relax the sphincter muscles.
A blob of Vaseline applied before a bowel movement can help to reduce the irritation of stool passing by the fissure site.
Some people find it soothing to sit on a heating pad (make sure it's on low) or a hot water bottle. Ice can also relieve inflammation and pain, just don't apply it directly to avoid tissue damage (cushion it in a soft cloth) and apply for 10 to 15 minutes at a time and then remove it.
Ibuprofen can at least take some of the edge off the pain in some people.
Lots of warm baths, lots of rest, no straining, healthy eating, soft stools, and focusing on relaxing the muscles in your anal area that you do have control over. Though the main problem is with the spasming of the internal sphincter, most people are also unconsciously clenching other muscles in the area as well. Deep breathing, filling your lower abdomen with your full breath will help you relax these muscles.
I hope you start to feel relief soon. Keep us posted on how you're doing. Everyone here understands the pain and the desperation of this affliction, so you're definitely in the right place.