Get a CT scan and MRI done, I had this issue and it was diagnosed so far as a Pineal Gland cyst. Pinealcystoma
The following answer was for a similar condition so you might find some irrelevant things,but the treatment in your case is same as described below.just read the treatment.
The condition seem to be pretty much a sphenoid sinus.I know you must be pretty fed up with doctors and you have a good reason for it.They are not doing what people think they are supposed to do.
Do you have headaches often due to this lump?Does moving you head right left ,or walking briskly or running cause pulsating pain?And as you described you have multiple infections including ear.The case seems to be sphenoid sinus.This sinus is often misdiagnosed.And condition left for long without being diagnosed causes infections as stated.
You can have a ct scan of paranasal sinuses to confirm the condition.Thought doctors need to have proper knowledge and suspicion of condition.
Now the cure is easy.You don't have to go to a doctor.
You should do sutra neti.here is the link.
Read the whole page.Search for sutra neti.It is a yogic kriya.Very simple yet very powerful. It has no side effects. Do it as told on this website. Following each step carefully.This is most likely to cure your condition and that too very fast.The moment you do it you will notice it. You should do it regularly for at least 3 months. It takes hardly 3 minutes to do sutra neti once you have learned it.Ypu can buy sutra neti and neti pot from amazon or ebay.In beginning use rubber one then cotton neti.Always do water/jal neti(stage 1 neti on website) after sutra neti.Do sutra neti and stage 1 neti which is water one for your condition.You can try other though not compulsory.
If you ever want to thank me,just teach other neti too so that they can benefit from it.