What Is Causing The Red Painful Bumps On My Torso?

In the past month or so, I've continually been having red bumps appear on my torso (upper sides, lower abdomen, back, etc.), which last for 2-3 days and then go away. The bumps initially look like they could be deep blemishes, but they don't hurt like blemishes, in that they don't feel hard or as if they're painful because of pressure in the blemish. Instead, they hurt more like a bruise when touched. I thought the first one I got on my lower abdomen was a spider bite, but now that I've gotten a total of about 5 in the past month, it seems less likely to me (I've checked the room thoroughly for spiders). Interestingly, the initial one did leave a scar that appears to be a very light bruise. Any thoughts? We did buy a new comforter about 1.5 months ago and I have noticed the microfiber has been coming out (it was cheap), could this perhaps be an allergy?