I have to take dolcolax (25mg), miralax, (polyethylene glycol) and linzess daily for severe constipation. Can I still get pregnant? Are they related to pregnancy at all?

Unrelated. but the bowel issue needs attention. Regular habits and Adequate water, prunes, natural should get you off formal laxatives? Consult with gastroenterology to be sure no other significant bowel disease, obstruction.