Ive had bilateral lumps in my armpits for 3-4 weeks. i think theyre lymph nodes. very painful to touch. constantly changing size, will get big and painful then shrink, only for the other side to become big (marble size) and tender. no other issue?

Reactive lymph nodes can be tender but they are almost always get smaller and resolve by times. They won't get big, shrink then reappear. I wonder if you can see these lumps or you just feel them. If you can see them, you may have hidradenitis suppurativa. You should see a doctor for a correct diagnosis; however, the manifestation is not consistent with a malignant disease.