I woke up with lots of bug bites?

So I woke up this morning and I discovered I had bites (similar to mosquito bites) all over my abdomen, back, hips, sides, and groin area. They itched extremely bad, and I ended up counting well over 25. I'd really like to know what cause all these bites. I just stripped my bed to look for bugs (and to wash the sheets) but even after looking with a magnifying glass, I didn't find anything. What could this be?