I'll try and keep it brief

Root canal failed, referred to endodentist who redid it. On this day lump appeared above tooth and in a lot of pain. This never went away. Endodentist did not care, went to normal dentist who said it was healing. 6 months later pain worse and lump was now huge and leaking out some sort of pus. Begged dentist to extract and he eventually did reluctantly (and said he believed pain was in my head)

2 days later lump and pain were gone and i felt 100% better, had been fainting and vomiting but was now back to full health.

Well fast forward one year, was feeling ill the other day and then i noticed lump was back! (same area above the missing tooth space) and is leaking out pus.

Im reluctant to go back to dentist after him not believing me about pain and saying lump was probably something else like sinuses or saliva glands (did go to GP by the way and she said he was wrong). Now he will say i told you so and not help me. The thing is lump did go away 2 days after extraction having been there for 6 months so it must have been related to the infected tooth. Right?