1. Is any more HIV testing required looking at my symptoms? Is there any subtype of HIV which could not have discovered by these tests.
NO...your test is 100% conclusive. So despite whatever "risk" you think you had (which you didn't, condom protected sex is safe sex...and you would have known without a doubt if the condom failed, it isn't something you miss)....your test proves you don't have HIV.
2. Can there be any other sex disease which is causing these symptoms? What can those be, for which I have not been tested?
If you have been tested at a clinic for all STD's, then you are okay. Refer to the clinic where you had your testing to see if everything was tested for.
3. What other tests should I go for in order to find a cure for my problems?
Your "symptoms" are not due to HIV, and most likely not related to any other STD, as it seems you were thoroughly tested. Therefore, if you continue to experience symptoms, work with your doctor to find the cause. It is not HIV. A lot of it sounds like anxiety, which in that case...the symptoms will start going away as soon as you start addressing the anxiety...with a professional if needed. .