Hi I had the same about 2 years ago and it lasted 6 months it was awful...it was all I could think about most days, I feel so sorry for you to have it while you are pregnant🙈
I didnt go to the docs and tried to cure it myself, which was very hit and miss, but here are the things that finally cured me.
The spasms are the WORST and actually could be more painful than the shitting glass feeling! I read this tip on reddit to ease the spasm and for me it helped immensely.
So just before you imagine the spasms will start you start blowing your lips out like a horse.....sounds so bloody weird but it really did work for me and i think the more your bum gets a rest from the spasms the better the fissure will get as you wont be as tense. If it doesnt work the first time keep trying and Im almost certain it will work. It gave me about a 50-70% reduction in pain.
Second thing that worked for me was having a spoonful of coconut oil daily. It’s definitely not an instant cure but after 2 weeks I think it started to make a difference. I would perhaps check with the doctor if you are not sure about taking it while pregnant and I would maybe take a spoonful every other day to begin...see what your tolerance level is.
The last tip might not work depending on where your fissure is...but might still be worth a try. My fissure was at the top near my tailbone...when i was having a bowel movement i would put some tissue around my hand and press on the area above my anus...not the hole but still in the crack (sorry about the images im conjuring up) this seemed to help the poop to come out from the pressure of your hand rather than the anus doing all the work so to speak🤣 I sometimes still do it even though the fissure has been gone a long time, as I hear that fissures often come back and it just generally makes bowel movements very easy.
I hope the tips work and good luck with it and your pregnancy too x