so confused and tired 😢😢

I went to the ER yesterday because I'm inpatient 🤷🏾‍♀️. They said blood and urine came back negative but I did have a cyst on my right side that was causing me what I thought was implantation pain. Yet I took a dollar store preganancy test before I went and it came back positive I took one today and it's super super faint but there's something there? I think I'm going crazy 😳. How can these test show even a little bit of a second line if I have no more hcg in my system from my miscarriage?