It's itching because it's trying to heal, so although it's difficult to bear, take it as a good sign not a bad one.
Here are some things to try to get the healing going strong.
Get yourself a peri bottle, which is just a spray bottle made for use "down there" with a sprayer that has a more ergonomic reach or is designed to spray as effectively upside down as right side up. They sell peri bottles at CVS, Target, and other similar places, certainly including Amazon. (There's a good looking one called a "Momwasher," with a sprayer that bends upward like a checkmark at the end, so you don't have to hold the bottle lower than the sprayer to use it.) If you can't get one, any spray bottle will work as long as you clean it really well first, but I do suggest getting one for the particular use we're talking about.
Make a saline solution, easily done at home. Here's a good explanation: https://www.healthline.com/health/make-your-own-saline-solution#how-to-make-it Use non-iodized salt (I had to make saline the other day to put on a bandage for a burn, and just used some Kosher salt we had.)
Once you've got your solution and your clean bottle, fill the bottle and every single time you use the loo at home, (and if you can manage it at work), spray your perineal area with the saline solution. The fact that the water has about the same salt concentration as is in your blood or tears keeps it from stinging. Spray every time or as often as possible. It should heal the area, and will be a huge relief also every time you spray there.
Additionally, to help keep the area from being so painful, you could wear a panty liner all the time, and change it every time you go to the loo.
You could also buy a tube of Neosporin (the cream version vs. the ointment version is fluffier and would be easier to apply to your raw tissues). After you use the loo, spray the area and pat it dry with t.p., apply a little Neosporin cream to the area. (You might even buy some of that cotton-based toilet paper, or the "natural" kind that doesn't use bleach, while you are healing.)
You also might consider moving to a really mild clothing detergent, like those sold for washing a baby's clothes, for your underwear. Wear only cotton underpants, and if you can go commando in the evening under a robe or skirt, do that.
All of the above should keep the abraded area clean, and that will seriously be 95% of the battle to it healing. I assume you aren't worried about an STD, or you would have mentioned it? So it's just a matter of getting the area clean enough to give it a chance to heal.
Good luck! You'll be amazed how good a saline-solution rinse can feel.