Diabetic with a bug bite of some sort.

Check the bite very carefully to see if it has one puncture mark or 2 side by side punctures.  Most insects have 1 puncture.  A spider will always have two and is sometimes hard to see.  Check for spreading redness and/or a hard lump around the bite area.  Both can be indications of a spider bite.  Black Widows, "Spindlers" and Brown Recluse are really bad this time of year and like to reside in dark areas.  They are also notorious for crawling in beds and are attracted to body heat & sweat.  Most spider bites require antibiotics or some type of advanced medical treatment (especially for diabetics - been there/done that...).  DO NOT try to lance the bite yourself since it can cause anything injected by whatever bit you to spread plus it can also cause a more serious infection if done wrong.  Strongly suggest that if it still itches after 3 days of being bitten that you seek professional help.  It's better to have piece of mind now than a hospital bill later.