My lymphocyte has been droping from44 to 28 in four years. could this be sign of having hiv?

No: HIV would have probably dropped it far lower. Lymphocyte counts actually fluctuate wildly even from hour to hour. However, the fact that you asked this question tells me you have some reason to be concerned about having HIV, and this is itself a reason to be tested. In most countries, it's considered wise to be checked yearly if you're dating at all. Best wishes.