How could this happen. I'm way too young. What do you think?

I was suspecting my period on Wednesday, the day before Thanksgiving. I normally get it that morning. And I didn’t, so I took a pregnancy test when I woke up and saw I wasn’t bleeding, because I had symptoms before that. I was nauseous, and had a couple other symptoms. The symptoms stopped a couple days before I was expecting my period. That night [Wednesday night] I noticed some bleeding in my underwear, but not enough to call it a period. So I figured I was just starting, and I went and put on a pad. Later, when I went pee, I noticed there was barely a spot of blood on it. But when I wipped after I went to the restroom I noticed there was blood on the toilet paper, but it wasn’t coming out enough to get on the pad. The pregnancy test I took was negative, but I wonder if it’s possible that was because I tested before I missed my period, like on the day I was expecting it. It’s now Sunday November 29th, and I haven’t had any bleeding. I have however had bad cramps in my low low stomach, they sometimes feel like menstration cramps, but they’re worse. They get better when I lay flat on my back. They usually start to hurt when I’m on my side or stomach. I’m on birth control to make me have my period, because I have irregular periods I need the birth control to make them come, my mom told me a while back that the birth control wasn’t as strong as the normal stuff, since it’s only for me to have my period. I don’t know if that’s true or not. I also wonder if since I missed a day in my pack this month if that could be why my period was late. I still would have gotten it though, and I haven’t. So I’ve ruled that out. Though my symptoms of pregnancy went away before I missed my period, I still had them. What do you think?