What is biting me?

Several weeks ago my partner and I were bitten by an insect. The bite was painless and seemed to happen while in bed. The bite was slightly raised like a mosquito bite, but barely visible. After a few days it became just a tiny pimple . It became very itchy and the itch lasted for weeks. I put fly paper by the bed and sticky traps under the legs but found nothing. No blood on sheets and nothing visible on the sheets which are changed weekly. Bites were mostly on shoulder chest neck area, but also some on torso and legs. Only a bite here and there no clusters.