Since i started my period i keep feeling nauseous throughout the day for the last 3 days. i am also constipated. but what is this and how can i get it to stop?

No other disease?: Each person with constipation needs to be sure there is no other disease causing it. If constipation is just due to slow movement of the food and poop through the gut, then the things people usually try are vegetables, water, prune juice, prunes, fiber-with-water, polyethylene glycol, Senokot or other senna, milk of magnesia, other laxatives... One's primary care doctor can evaluate, if needed.