General doctor is sending me to an infectious disease specialist, for getting swollen lymphnode and sick a lot... what will they be looking for? hiv?

Yes: And other conditions too affectting your immune system. Screening / diagnosing HIV infection isn't a problem nowadays, hope you don't have it if you don't have the risk factors. Other common possibility is chronic infectious mononucleosis, uncommon , but need to be ruled out, a more detailed analysis of your immune system after more history and physical examination would be carried out, goodluck

Yes, also...: Yes, they will look for HIV and other chronic infections such as Lyme disease. They may also look for conditions like immunoglobulin deficiencies. You may also have nutrient deficiencies; you are likely deficient in Vit D unless you take it. All adults should take about 5000 iu of D3/day in fall & winter. Take a quality multivitamin and eat a healthy diet, minimize sugars and junk food.Good luck!