There are 2 issues here:

Are these really bites? And how well did you look for bed bugs?

Even if these are really bites, these could be due a spider, centipede, bird mites, fire ants, etc. Or these may not be bites but an allergic reaction.

When you have a skin reaction that appears to be a bite, there are other possibilities than actual bites. Like environmental allergens. Even if there is not a change in the environment, it is us that changed with time. Things that did not cause allergy in the past, do now.

So there is a process of elimination that takes observations over time to reach a solid conclusion.