Hi, under my armpits I have like redish pimple looking things and they hurt and when I pop them pus comes out and sometimes blood. They always come bac?

Armpit pimples. You may be having a chronic bacterial skin infection. You should see your doctor for an exam and a culture if required. You may need antibiotics to clear this up.
Folliculitis? This could be stardard folliculitis, i.e. pimples or boils that start in hair follicles. It can be triggered by shaving. However, there is a chance you are in the early stage of a condition called hidradenitis suppurativa, which it advanced stages can be difficult to treat. You should see your doctor, or perhaps a dermatologist.