Are you on iron tabs? I was vegetarian when pregnant and got put on them - one type gives you constipation and one doesn't - ferrous fumarate I think is the good one
As PP said, ludicrous amounts of water, copious fruit and veg, limit gloopy carbs like bread, cake, pasta etc. Have wholegrain versions of things so brown bread and rice, wholemeal pasta.
Have flax/linseed or chia seed soaked in water overnight then you drink it down - it goes slippy and helps. My breakfast is usually oats and chia soaked overnight in whatever milk you like, add yoghurt, nut and berries etc in the morning - totally botty blaster!
Lactulose and dried fruit too.
I know it's not always what you feel like when uncomfortable, but a good walk can help to move things along as the motion massages your guts. If you can't face that, get on your hands and knees and circle your hips around a bit.
It's nothing to be ashamed of, constipation in pregnancy is very common but not something people talk about much. It's sadly also common after birth so stock up on lactulose, dried fruit etc! I ended up with anal fissures due to constipation after birth once and I really, really do not recommend the experience.