What Causes Heaviness In Abdomen While On Contraceptive Pills?

Hi I am having a heavy feeling in my uterus. I was sexually active on the 24th but I'm on BC. At the time I was on the sugar pill week. I'm only on my second pack so I'm not sure if it's that. I was on Zovia but then CVs gave me Kelnor. i took a test but apparently nothing works and nothing at all showed up. does it sound like I'm pregnant or is it too early to tell?