Hi A faint positive pregnancy test followed by a negative blood test rules out any possibility of pregnancy. But then you might carry out another blood test to confirm that there is no pregnancy for now. Constipation with Cramping and fatigue indicate you are having problems related to improper digestion and diminished absorption capacity of the digested food towards your Liver and leading to low energy levels in-spite of eating ample and good quality food. You might also be facing these problems since some months and they have ultimately shown up on your body in the form of irregular periods, hot flushes, constipation, cramping with fatigue.