What kind of bug bites are these?

In the past couple of nights, I've gotten mysterious, itchy welts from either mosquitoes or some other bug/insect I can't see in my bedroom. This has happened throughout the day, not just at night. I've gotten bites from sitting at my computer desk and sitting on my bed. The bug bites range from very small (the size of a hair follicle) to a large bump like a mosquito bite. Most of the bites have been on my legs, arms, and shoulders. My bedroom has five windows and I know sometimes bugs get through the cracks. Could these just be mosquito bites? Or bed bugs, chiggers, etc.?