Insect Bite (?) healing slow

Hello!  I have a question regarding what I assumed was an insect bite.  During the past two summers, I've discovered round bumps that look like mosquito bites on my body.  They itch like mosquito bites however they last for much longer than mosquito bites I've ever had before.  Also, when I scratch them (being unable to contain myself), they ooze clear pus from what appears to be the bite hole.  A scab does form, however if I scratch is again, the swelling contiunes to ooze and retains heat, with the swelling remaining for a period of up to 3 - 4 weeks.  After a while, the site will heal, however wether I scratch the swelling or not, it leaves a scar with a small, pin-hole size spot at the center.  They're unlike any mosquito bites I've ever had before.  I would appreciate any information!