I suffer from fatigue and body pain for 2 years… is it STDs or cancer?

Hi Doc,
I am a 28 yr old male, for the past 2 years experiencing various symptoms like Fatigue, Body Pain & Bumps. My major & frequent symptom is fatigue & body pain, initially this occurred 3 to 6 months once but now it’s like once in every month. Once the symptoms start to hit I will feel very tired and whole body will be in pain like I am going to have fever, it will continue until a week and goes off after that no use even if I take paracetamol it will remain for 1 week and goes off itself. Beginning I thought I had some fever but the hospital I visited mentioned my temperature is normal, I had consulted one or more doctors who had concluded me that it’s because of STRESS. I have been tested for CBC (Full blood test), Thyroid, Ultrasonic for kidneys, VDRL, Hepatitis and even HIV where all turned out to be normal. More than once & in different period of time I got tested for WBC where the doctors said I have no infection and all my counts are normal. For record I had sex with protection in the past.
Over the past 2 months I managed to change my lifestyle like extending my hours of sleep to 7 & half hours to 8 hours (Before I used to sleep only 6 hours max.) and working out my body 5 days a week. But still I am experiencing the symptoms more often unlike before as the fatigue & body pain now started to occur twice in a month. I am totally confused & annoyed and no idea in what direction I should move forward like should I continue to look out for more tests on STD types of diseases or else should I test for cancer or any other tests. Kindly be advised.