What Causes Constant Nausea While Sexually Active?

I've been feeling very nauseated and it's making my mood completely off the longer I have it, If i eat more than three times a day to make my stomach calm I still feel nauseated and If i eat normal I feel it too. I'm sexually active but have been being safe about it. I had a spotting on the tenth and usually start on the 21st and nothings happened. The spotting only happened once on the tenth and nothing now. I don't know if there's signs I could be pregnant or if there's something wrong with my stomach. I took a test but it was one I was suppose to do before my expected period and I took it at the wrong time. Does that matter? The nausea feeling has been going on for a couple months now and I don't know what's going on.