@Hbw18 there are good stretches online which help. I find sitting cross legged, and putting my outside foot on top of the knee and then leaning forward and to one side helps (double pigeon stretch I think it's called?)
Also get someone to massage your glutes firmly, or you can use a tennis or lacrosse ball and sit on it.
And get up every 20 minutes to stretch/walk around if you can. Special donut type pillows can help for sitting in work.
I referred myself to the hospital physio. Thought it would just be a one off appointment but it's been really good, I'm under the pregnancy physio and have regular appointments up until I give birth.