Is ELISA Test Reliable For Detecting HIV Infection?

Dear Dr, .Will you please answer to me this time? I had sex with one philippino sex worker on Oct-2010.After a week i got symptoms that rashes especially on chest and upper part of the body,too much fatigue,abnormality in sleeping,bad constupation. After 2 months one of my lymph node below the ear become swell and it is continuing still now.I have improper digestion now,i am going to bathroom more than 3 times a day.But it is not going good.My stool appears as water with small round like items.I have oral ulsers now under my tongue.And also i am geting rashes irregularly.I tested 4 times with ELISA antibody/antigen method,the results were negative.The details are as follows At 5 weeks-ELISA AB/P24ag Negative. At 8.3 weeks-ELISA AB/P24ag Negative. At 16 weeks-ELISA AB/P24ag Negative. At 26 weeks-ELISA AB/P24ag Negative. I also my tested my blood for CBC,Liver function tests.The lymphocytes count slightly increased.I am feeling as tired now. I took the vaccine for chicken pox on May 2010. Dr Bob,I have these doubts. 1)Are my tests reliable and conclusive? 2)Do I need further testing? 3)Does the chickenpox vaccine affects the test results? 4)If the tests are reliable,then what is the possible thing for the swollen lymph node?