Hello and congratulations, I had a very similar situation to you. I had no periods, was on a massive weight lose regime, told it was very very unlikely I would get pregnant after trying all the usual interventions except IVF.
Weight loss stopped, and I started to get a pain at to of abdomen. Stomach looked swollen. I got examined by two doctors (twice) who both said it was likely to be a bowel blockage and anything I was feeling was that.
Finally I was in tears at 4th doc appointment and she agreed to a CT scan. But it was late in the day and she said I had to have a pregnancy test as I was female but it would be negative but I had to do it. Went home did test later on it was positive....
Got another at 10pm it was positive. Shit. No sleep that night. Went to fix first thing and doc from previous night was on way out to house calls. I screamed (yes whoops) it was positive. She stopped, stared and then organised an appointment with the other doc (who had seen me twice).
Went to him, he examined me and said well you won't be far gone and booked me an emergency ultrasound. Went up to hospital and I had the scan I was 30 weeks and 3 days. I went into shock for two weeks and I really don't remember any of it.
I had a very tiny baby at 37 weeks due to hellp syndrome, caused by (we think) stress of that and other things going on. She is now a very healthy 4yr old.
So please dm me is you would like, is not identical to you but I really understand the shock. If you need to find someone to advocate for you and just take some time to get your head around this. All the best. Rat