last night when I felt itchy on my back during sleep, tried to scratch it and felt painful like a bruise. Today i woke up with a few bites on my back, they are not that itchy or painful, but when I put Benadryl cream on, they were burning like crazy. Later I tried apple cider vinegar, it hurt like putting alcohol on a wound. Then after couple of minutes of applying apple cider vinegar, the worst one oozing yellow liquid. Now I just feel a little of pain on my back. What can be these bites?