Traps stay empty, but bedbugs remain...

After subletting my apartment I discovered some bed bugs (one living, and around 7 dead ones) in my bed frame. Long story short, I washed everything, showered after and before bed, put my mattress in a bed bug cover, disassembled my bed and cleaned every board and screw with hot water in the shower, and reassembled it far from the walls, with nothing overhead, to be safe I also sealed the gaps between the floorboards. Most of the clutter in my apartment is sealed in plastic bags, including all of my clothes. I even installed two kinds of traps, some that go around the feet of furniture where supposedly they can crawl in, but not out, and a second kind that attract them via smell and trap them in glue.

None of my traps have caught one since I laid them out three weeks ago, and no visual searches around the bed frame, mattress and the rest of the flat have turned up anything. Great, right? Unfortunately, I still get occasional bites that are unmistakably those of bedbugs. I'm absolutely clueless as to how (maybe one survived in the bed frame, or the encasing is not working, but that seems unlikely as the bites were in spots impossible to reach from within the encasing.), and I would feel super stupid to spend hundreds of bucks on an exterminator, when it seems like I can barely proof that I still have them. Besides, I'm uncertain they would be able to eradicate them (maybe I'll have to buy a new bed and mattress anyways).

Anybody here that has dealt with a similar situation? Any advice or tips, specifically for more reliable detection traps? I'd highly appreciate any help.