Hopefully you'll find this reassuring, I was in a total panic when I had my results but honestly it has been nowhere near as scary as I expected.
I had CIN3 and CGIN (which is changes to the cells inside the cervix) diagnosed in 2020, I was seen really quickly at the hospital and had a cone biopsy same day - which I wasn't expecting as the leaflet they had sent me said it would need to be done under general anesthetic, but it was done with local. I was uncomfortable but not in pain and was given gas and air to relax. The appointment less than 20 minutes in total and the results came back in less than a week.
The healing was a bit strange, not painful but itchy! And because the tool they use burns away the affected areas you will get little black bits in your discharge. I did find my periods to be a bit more painful for the first couple of months while I was healing, and you can't have sex or go swimming or take a bath for a few weeks.
Unfortunately, they didn't get clean margins on my biopsy but had already removed quite a large section of my cervix. I was offered a hysterectomy at that point, but I declined as I was only in my 20's and had been trying for a baby. I could also have chosen to have a repeat cone biopsy, but it would have meant removing about 90% of my cervix and meant I wouldn't be able to carry a pregnancy. I now have a smear every 6 months at the hospital where they are monitoring me for any changes but so far everything has been fine - this will go on for 10 years, unless they detect any further changes before then. If I hadn't wanted children or had already completed my family, they would have strongly recommended hysterectomy.
I'm due my 6th checkup soon and honestly, it's fine, I see the same doctor every time, they do the smear, she tells me how nice my cervix looks and I get the results back within 2 weeks.
Please try not to worry, I know we all convince ourselves of the worst-case scenario but it's incredibly unlikely you'll have gone from a clean smear to cervical cancer in 3 years. Most likely is you'll have your treatment and get the all clear, but even if you're like me and don't get the all clear there are options and really robust treatment and monitoring available, it's nothing to be afraid of.
Good luck with everything x