can i consider my immune system is still strong?

Hello and welcome to e health forum.

Since the ELISA tests have been negative, the exposure, 5 years back did not cause any form of infection to you. ‎

Your test results are conclusive and indicate that you do not have HIV.‎

Once a virus, is detected by the immune cells of the body, antibody synthesis is initiated and it persists ‎as long as the virus is active in the body.

‎‎97% of normal individuals with a good immune system, produce antibodies within 4-12 weeks and the ‎remaining (3%) might produce the antibodies, around or after 6 months.

In case you were infected in reality, then the antibodies would be in higher titres and you would have had severe manifestations of HIV infection by now.

CD4 count is a separate estimation of lymphocytes measured via flow cytometry and is completely independent from the complete blood count, and it is not calculated based on the lymphocyte count. ‎

Your immune system is completely in normal condition (as shown by the blood results) and there should not be any form of doubt about that.

You do not have HIV antibodies in your blood, as you are not infected in the first place.

You need not be worried about your past, but you need to be cautious about your sexual behavior in ‎the future. ‎