So frustrating...

Alright so a few days ago, I got fairly faint but clear pink double lines on THREE first response tests. Well, I made an appointment. I took one last night to make sure and it was an 88 cent test from Walmart, but was darker than the one that I had taken before I even took the first response tests. Well, I went to my appointment, filled out paper work, and waited for the results. She came back and said they were negative. I was confused and showed her my tests and she was really confused as to why her test wasn’t picking it up.. so she ran it again with the little bit of pee I had left. Came back negative again. She told me to wait a week, and if I still hadn’t had my period then to come back. My last period was November 22nd so I felt pretty positive that it was gonna show up positive for them.. I’m kind of worried at this point. I haven’t had any bad cramping or any spotting or anything. I’ve had pregnancy symptoms such as headache, nausea, dizziness, sore boobs and nipples, and increased discharge. What do you think it going on?? She really had no idea what to tell me.