I had this in my first pregnancy, and work were really hard on me. I worked in an old building on the top floor, stairs all the way and the loos were in the basement. It was unbelievable pain. The car park was a huge distance away and one evening I was in so much pain I had to stop and sit on the kerb in the rain, it was agony. A student took pity on me and picked me up and took me to my car. I cried and called DH as I couldn't face driving home in that pain and he came and collected me. I went to the GP's the next day and was signed off for a month at 26 weeks and given some great pain relief. I did go back for a little bit until my ML started at 39 weeks, I felt awful, but it really is best for the baby that you don't put your body under that kind of strain.
I hadn't got any help before then and had suffered on thinking it was normal. I wish now that I'd got some support earlier, the MW's just seemed to brush it off, whereas the GP who is normally a gruff old grump was really understanding, not only referring me for physio but happy to sign me off, I thought it would be hardwork getting any support.
Physio ended up being a more therapeutic massage and manipulation, by that point there wasn't any exercise that would help. I used to go to the local pool for a float about, even attempting to kick my legs really hurt, they used to play some nice relaxing music [wind-down hour] and it was a real relief to my sore pelvis.
I was worried about delivery, but had a relatively straightforward delivery and was walking without pain within a few days, gently, but it was such a relief.
I started Pilates when DD was 6 months old and it really has helped. I am 21 weeks pregnant with No.2 and my pelvic pain is very miniscule in comparison to last time.