These are most likely bed bugs stings…
There are bed bugs, who normally feed in a straight line of 2-4 bites. Check your mattress, specifically seams and other places that are dark. Also look for dried blood in those same places.
How to get rid of them
You should seriously get a bag of diatomaceous earth, food grade.
You can literally eat it with a spoon, but for bedbugs, it’s like a razor blade. They crawl over it and die very quickly. It’s not that expensive, either.
Of all the things I’ve used to get rid of them in my dad’s house, this worked best by far. You can literally just poof it out everywhere. Only thing to worry about is when you hoover it all up. It can wreak havoc on some vacuum cleaner motors.