Could it be lymphoma?

I came down with flu round early June felt bad fatigued etc. The flu went but the fatigue lingered and is nothing like i've experienced before in the past and coupled with headaches. I'm concerned about Lymphoma as I have had joint pains in my left leg(where the lymph nodes are), for about a month or longer. I'm worried it is a swollen node. I also have lumps on my neck, however I was told that these were just glands and I've had them for years. I'm worried that this flu has masked something more sinister.

The pain in my joint mainly hurts when I move that part. I've gone to the doctors multiple times as the fatigue has affected my quality of life, but tests I have come back normal. What tests have done is the following:

Blood test - CBC, cortisol, creatine, LDH - all came back normal

Chest X rays (recent)

Past tests:

Echocardiogram (while back)

Endoscopy (last year)

Colonoscopy(last year)

ECGs (while back)

Though these have come back normal, I'm worried that I still have not recovered and these pains in my joints could indicate a problem with the lymph nodes. Is there anything I can do to get the doctor to investigate this?