Anaemia is not contagious. However several infectious diseases which cause Anaemia can be contagious. But most of the STDs dont cause Anaemia.
Stop blaming your girlfriend and do a full Anaemia profile with includes CBC with morphology, Iron profile, Vit
B12 &Folate serum levels, Billirubin to rule out haemolytic anaemia, Stool R/e to rule out Intestinal parasitic infections
Next Steps
Take Iron, VitB 12 and Folic acid tablets regularly
Review your Hb reports after 3 months
Health Tips
if your Hb level is below 10, visit a hospital asap