Pests infestation in bathroom – identification and termination

Sounds like bed bugs to me. Have you, or anyone else, noticed bite marks? Sleep with a flashlight near the bed and if you wake up at night, use that to look for them (too much light will scare them away).

My suggestion is to strip the bed of all linens and wash them (you need heat to kill them, hot water and/or hot air from the dryer). Remove and check the mattress and box springs and then check the entire bed frame. Eliminate any paths from the bed frame to the wall or floor (placing the feet of the bed in a bowl of water or some other boundary). Put the mattress and box springs in a zippered cover. And finally, use a bed bug spray to kill any that make it through all this. Note that these things can last a long time, so don't let down your guard for at least a year since you saw the last sign of them.

It's hard to give accurate advice without more information about the building. They've got to get in from the outside, but they can get into your room though an attic, crawlspace, etc. Go outside and look for openings. A common place is where the electrical service enters the house through an attic. If you go out in the middle of the day, you should be able to see them flying around.

The house I grew up in had a HUGE bee infestation in the attic. They got in through soffit vents. Every once and a while a couple of bees would come into my room through openings around the A/C register. No one figured out that they were coming in from the attic until honey started dripping through the drywall ceiling (my mom had first blamed me for spilling something sticky on the carpet). They had to go in and out to feed, and we did notice them outside, but we did not think they had actually nested in our house. They were much more evident outside than inside.

So, with this experience, I say take the time to observe them from the outside to determine where they are coming into the building structure, then search for nests.