Helloooo. Quick history. I'm a female in my late 20s. No children. I've had an anal fissure since November of 2011. I had no health insurance at the time...not to mention I was completely confused and humiliated.
Near the end, before I was finally able to go to the doctor, I was only going to the bathroom every 5-7 days because I was terrified of the pain. But I don't need to tell you guys. In December of 2012 I finally went to a doctor, who confirmed. He gave me a list of things to do and it's gotten much better. At one point I thought it was almost all over...and then it tore again, a little. Since then things have been weird. I'm still having pain but it's different. And there's very little blood. I almost feel like I've healed to tightly. Too small. Is that possible? I feel like I have to push really hard, almost to the point of passing out and seeing stars, to finish a BM. Put the pushing hard isn't because I'm constipated. And, like I said, it still hurts. Is this just a process of my healing? Or something wrong with my muscles/rectum and should I go back to the doctor?
I do have the nitro, which I've only used twice because A.) It hurt too much trying to put it in and B.) It made be dizzy.
As you can see with me having waited so long...going to the doctor is an overwhelmingly sensitive issue for me. And I don't want to go back. So I wanted to see if anyone has had a similar experience...see if any of this sounds familiar.
Thanks. :)

Do you use miralax? I would doubt its possible to heal to small but the muscle remaining to tight would certainly give that feeling. I use the nitro and as you heel the burning lessens, I notice shortly after using it my bum is more relaxed. On another note I believe if you can work on shifting your mind from being sensitive about this issue your body will be more receptive to healing. I got over the sensitivity issue some time ago intent to just heal. I am in my mid forties which is different chapter than my mid 20's but you have taken a good step tuning into this group.

Yes. Your body can heal too small. Another way of putting that is that less flexible scar tissue can develop to the point where the opening is too narrow.
What you are describing may or may not be a too narrow opening. Obviously, I'm not in your body, but it sounds to me like you might be getting spasms in your anal sphincter. Almost everyone on these boards gets spasms. They are very common with AF. There are lots of stories on these boards about how people have dealt with there spasms.
Two obvious things. Please, stop straining to poop. I know you think your body will only poop if you strain. I was there too. I thought people were nuts when they said not to push. I used to push with every poop. For me, I learned how to not push when I discovered squatting. It turns out that my anatomy is wrong for sitting while having a BM. Squatting "cleared the runway" so that my stools could escape easier.
It sounds like you need to work on developing healthy BM habits. A healthy body should have a BM every single frakin' day. I'm not exaggerating. Every day. Its bad news if you miss a day because your body will be sucking the water out of your nice soft poo and turning it into a brick, which you will then have to give birth to the next time you finally get to the toilet.
I would suggest exploring the idea of using miralax and changing your diet. There are lots of opinions around what makes the perfect diet, but you'll notice some trends. No junk food. Less or no meat. Lots of fruits and veggies. Some people need to eliminate certain foods, like wheat or dairy, all together, but that's something you'll figure out in time if you are gentle with yourself and listen to your body.
Use your nitro! A couple of tips: Don't put it in until you are looser. Just put a small amount around the opening of your bung hole. It will still work. Make sure you use a glove or a finger cot. You don't want the medicine absorbing into your finger, too. Lay down for 20 minutes after taking the nitro. The dizzy thing will pass. Dizzy isn't so bad. Some people get crushing headaches, so you are lucky that you are only getting dizzy. Believe me, the dizzy is so much easier than the pain after surgery. Please don't give up on the nitro if you don't have to. The surgery is no walk in the park.

You're in spasm. I'm currently going through this after healing. Not really sure how to stop it if I'm perfectly honest with you! I've had loose days and tight days. I think if I do something "naughty" like have an alcoholic drink or eat red meat, spices, etc I'm sub consciously worried about what the next day may bring.
I really need to get out of this cycle as its not healthy and also painful (like cramp!). If I manage to resolve the issue I'll let you know how I did it. :)