i would say it is anemia-----
you should get your doc to check your blood count.
Im naturally anemic but most women become anemic during pregnancy.
With my second bub.. i did reach the extent of passing out i wasnt able to go to place alone cause of the heat (i passed out in a take away shop once that was embarassing)
you should take Iron tablets,,, FEFOL is based on Iron, it also gives you the folic acid recommended for Pregnancy.
I recommend you take Vit C tablets also with these as some people tend to get bowel probs. if you know what i mean with the iron intake of fefol but Vit C breaks it down better.
Seek your doc. help if it keeps continuing.