Never ever in my life have i had any kind of allergies.however in my third pregnancy in 2018 i developed spring allergy,terrible swelling and itching of eyes for 2 months every year since then. will it ever go away by itself?

During the third pregnancy your body was exposed with certain fetus's contents and that event could create a cascade of immunologic reactions. Since then, your body had new antibodies against the antigens that you had not had before the third pregnancy which can explain the spring allergy in the last couple years. Unfortunately, this sensitization is likely permanent.