Mystery Bites that Won't Go Away

Hello,
About three weeks ago, my boyfriend and I noticed a couple of very itchy red welts on our upper arms when we woke up. This experience has continued and we wake up with at least 4 or five bumps each morning. They are primarily on the forearm, upper arm (front and back), chest, outer elbow area, and neck. The itching is terribly intense. We called an exterminator who inspected the bed and placed glue traps throughout our apartment. After letting the traps sit for a day and a half, nothing was apparent on the traps and he determined that we have body lice. We have since washed all clothing and bedding and sprayed all furniture with RID. I have done some reading on body lice, and it seems rather improbable that we would have them. We are both extremely clean in our home and in regards to personal hygiene. Bedbugs and fleas were not found, nor were mites. These bites are red and swollen, about the size of a dime, and are often in clusters of two or three. As previously mentioned, they itch and hurt! We live in a small apartment above a Persian rug store and below an apartment with at least 7 adults and 2 children in a small space. Is there a chance that something from either above or below could be the source? Are there any other "predators" other than lice, mites, fleas, and bedbugs that have not been considered? All suggestions are welcome! We are desperate for help!