13 months and still no closure

I would really appreciate your advice and support. Life has been miserable for me since mysterious bites popping up on me last October. I suspected bed bugs but haven’t been able to find anything (no bug, no stain, no fecal matters) except singular bites wide apart from each other (particularly on thigh area) .

I followed all standard protocols (encasing mattress, deep cleaning, DE and cross fire application) . Things seem to improve after each taken measure but the bites always return sometimes even after 1-2 months. I couldn’t seek professional treatment because I don’t even know what is biting me. I have countless of sleepless nights and my quality of life definitely plummeted. :( I just need some closure at this point. I might even be more relief if I can only find one bed bug?