Constipated

Hi all, New GD diet is going well and controlled via diet only. However, big side effect is the constipation and pain when I finally go as it's hard. Anybody know of any pregnancy friendly medicines to help? I used to have a huge bowl of high fibre cereal and a banana in a morning which obviously Iv had to stop which I think is making a big difference to my 'system' lol. I'm trying to eat other fibres but doesn't seem to be as effective.