Hi Bailey, if you've been on the nitro about 12 days, that isn't very long. If you aren't getting headaches, you could try increasing the amount a little, and see what happens. I can't really say how long it took. There were so many factors that had to come together - diet, getting consistently soft stools, discovering how wonderful a hot water bottle is for soothing and healing, plus the nitro. If you need a number, I'd say about a month.
I don't know about an internal fissure. You could have one, and the only way to know is to look inside. When I had my colonoscopy (just a regular 50 year checkup) they said they didn't see a fissure, but most likely would not have seen it with that method. I think generally they use an anuscope for that - but ask.
Honestly I don't know if a general surgeon could do the op. Maybe, maybe not. I'd look around for a very experienced CRS.
If it's any comfort, I went on the trip of a lifetime with my fissure. National Parks of the American southwest - Grand Canyon, Zion Canyon, Bryce Canyon, Capitol Reef, a road trip across Nevada, Lake Taho and so on. Plus we were camping! I won't say it was a bed of roses, and I was in pain and uncomfortable much of the time, BUT I still had a great time, and my memories of the trip don't include the pain, but rather the amazing things we did and saw. I even went white water rafting and enjoyed it. The following night wasn't so great mind you. But I'm still glad I did it. So take heart.