Pos and neg tests???

Saturday I didn't drink very much fluid, Sunday I got a FAINT positive and I drank a bunch of fluid, Monday I got a negative test and didn't drink very many fluids, this morning I got another FAINT positive. It takes about 5-8 minutes to show positive, initially there isn't a line. The test window is readable until 10 minutes. I got a surge on the 17th. My boobs are ridiculously heavy and have been sore since the 19th. Any ideas? Is it normal to get positive and negative tests? Can you get positive tests this early? With my first child I didn't test until I was 6 weeks pregnant so my line was a BFP. I'm trying not to get my hopes up. Does anyone have an experience like this? Any ideas? TIA.
The top picture is the line from this morning, the bottom is the line from Sunday morning. Also- I haven't had evap lines on any of these tests so I don't think they are prone to them.