Extremely faint line... could it be Evap?

after 6 weeks on metformin 1500 I had my  first ever normal cycle, during the middle of my next cycle I started the feel nauseous, and was sick in morning of 15/12/16 so tested. Got this VERY faint and BARELY even there line. Tested the next day with a clear blue digital BFN. Then again the next day with a pink dye BFN. Have had moderate cramping mainly in my legs, back and slight cramping in the 'womb' area for about 3/4 days. Have fatigue and don't feel quite myself but no more sickness. Still no sign of AF ☹️ opinions? TTCBabyEarle#2//metformin//ttc2years//