Fibergel is good and I think it is safe for use during pregnancy (but I would check the box just in case). You should be able to get it from any chemist (its in an orange box)
My doctor prescribed Lactulose when I was pregnant and 'having trouble'! It soften things up, if you know what I mean!!
Try Bran Flakes or Shreddies, they may help.
Okay...1ST CHECK WITH YOUR DOCTOR TO MAKE SURE THAT THIS IS SAFE FOR YOU! My OBGYN told me a secret: Coffee stimulates can bowel movement. She said 1-2 cups of coffee a day is perfectly safe during pregnancy. So she suggested to get up in the morning a couple hours earlier than usual, drink a glass of cranberry juice and a cup of black coffee without sugar. Then go back to bed and sleep for another couple hours. When you wake up, you should feel the need use the loo. It worked for me and I still do this when I have any problems.
Eat a small package of prunes and you can buy single packs of them to keep in your purse...safe for when your pregnant because it is just dried friut :)