Weirdness

Megan
So normally my cycles are pretty predictable. My period is regular every month (still is) it will last around 5-7 days, my bathroom habits were regular, I was healthy. 
Now, my last period only lasted 4 days, stopped two days, came back for a half day, then gone. I find myself constipated, it doesn't happen once a day like normal. And when it does I still feel backed up. I get very nauseous at random times all day then also when I'm hot. No vomit tho. 
I am married and have unprotected sex pretty much nightly with my husband. And it's been that way for 5 years. I haven't been pregnant even once during this entire 5 years so I doubt that's it. 
Does anyone have any ideas