Faint positive then negative

A few days ago I took two blue dye pregnancy tests and got a faint positive from both. I read about how those are likely to give false positives though, so I took one FRER the next day and it also had a faint positive. A few days later I took another FRER and it came out negative. Has this ever happened to you? My husband is very supportive and believes that I'm still pregnant but I'm worried that I'm not. Any thoughts?