Suggest Remedies For Extremely Itchy Pus Filled Bumps On Legs

I have Extremely itchy bumps which after few daya become darker and have a black hardened dot like thing. These black dots can be squeezed out. After which a small opening can be seen. These bumps sort of leave marks for days. Take few weeks to disappear. They are mostly found on my legs and feet. Sometimes on waist and arms as well. They seem to be insect bites, but i get them once in few months.. Checked carefully for bed bugs, did not find any. What can they be