Positive test?

Help. I took a test this morning. It was negative. I’m not due for AF until the 11th. My breasts hurt (which is normal before AF) but they’ve been hurting for 2 weeks. I’m crampy and my lower back hurts.

I emptied the trash this evening and the test is now positive? Is this normal? I know they say not to read them after so long but I’ve had other tests before that have stayed negative. Why would it even show that line if no hcg is detected? It’s a cheap-o year from the dollar store. Maybe just a fluke?