Desperate plea for potty training advice

I was hoping to some words of advice about our current potty training situation . Daughter born early December 2022. Almost 2.5. Started potty training 3 weeks ago. I had done a lot of reading on ERIC website and read that you should start before 30 months for bowel and bladder health. I’m also on maternity leave until July with second baby and it’s summer so thought I would give it a try. She didn’t show that many signs of readiness but ERIC website said that’s common and doesn’t mean they aren’t ready. Friends also told me same. Initially she did really well, barely any accidents, all wees and a couple of poos on potty. I thought we had cracked it. After first weekend she started holding her poos big time and was only passing hard boulders in her knickers every few days and complaining of tummy pain. I took her to GP and was given movicol laxative. Gave her this for three days and she started soiling with mushy / runny poo in her knickers multiple times a day. There was A LOT of poo. She now seems to have cleared out but is still only pooing in her knickers. I got sent home from nursery today with 8 pairs of dirty knickers from wee/ poo. She weed in her car seat on way home and then three times before bedtime. She seems to have majorly regressed. Iv tried no knickers. Iv tried stickers and charts, I read to her in potty, have let her watch her fave shows. I sit her on potty after meals. Iv tried bribery with chocolate, nothing seems to have helped. What would you do? Should I give up and try again in a few months? I don’t want to confuse her but equally feel bad for the poor kid just being in dirty knickers constantly!