I just dont feel right?

Within the past week I just haven't been feeling right. My fiance and I had a nice weekend away for his birthday. We stayed in a hotel one night and my dads the other. I had been feeling kinda icky and having some nausea. At the start of the weekend. After a physical day with my younger sister in an extreme laser tag event Saturday I started having light pink or brown spotting. I am on the pill and have been for years, I recently went about 6 weeks without being on it around the holidays, and have been back on it for about a month. My period is due Thursday or Friday so I figured the spotting must just be my period coming a bit early cause I had been of the people of so long before. But Sunday morning it was still just the spotting (not even enough to use a pad, just a little bit when I wipe). Now, Tuesday night I am still just having the faint spotting. I also have had some minor cramping in my lower stomach and the nausea is still with me. I was talking with my mother and she said it may just be a bladder infection (or a stomach bug going around at my younger siblings school) because my lower back is also kind of sore. But something just doesn't feel quite right, and I haven't been able to explain it to my fiance. I feel off. Can anyone help, my fiance and I weren't intentionally planning for a child at our age but know if it does happen it was meant to be by God. I'm just kind of freaking out that I might be, I've never felt like this before.