TMI But Constipated

Hi All, just wondering if any has been through or currently going through constipation. I am 22 weeks with baby #2 & never had this issue with first bub. Its getting really bad to the point I am going number 2s every 4-5 days & I am feeling so nauseous & very uncomfortable until I can go but even when I do go its still really hard to get out. I am also getting really bad headaches when trying to go to the toilet.

What can you take to get constipation relief whilst pregnant?