Hi. Do you have swollen lymph nodes? If you do, where are these located? What is the size of the largest one? What is the consistency of the nodes (hard, firm, soft, doughy, etc)? You have not explicitly stated it in your post, but I'm assuming that you do since you're concerned about swollen nodes and lymphomas.
If you do have swollen nodes, these may be due to a lingering infection. Is that abscess in your tailbone totally resolved? If you're still having recurrent low back pain, it may be due to a lingering infection in your back (abscess recurrence?). The possibility of recurrent infection needs to be ruled out first before even considering a diagnosis of lymphoma.