The ones on your abdomen could be from a flea infestation in your bed... they like soft furnishings where animals have lain. You may have brought in one from somewhere and it's happily living in your furniture. They prefer animal blood but will bite humans if nothing else is available.
Try a glue trap on your floor... a wide shallow bowl like a plant saucer, with something sticky like double sided tape or honey in it. The fleas jump in but can't jump out again. At least you'll be able to see what you're dealing with.
Have you an animal nearby that visits you? Any suspicious flattened, warm patches and opened windows you might not have noticed before?
Mosquitos will go for any visible flesh but fleas will crawl around inside clothing.