you suffer from allergy
it may be due to pollen or dust. it looks like it may be from pollen since its only during few months of year.
now to treat allergy you have to do it in a step wise manner
first if your symptoms is for few months a year like 2-3 months then you start an antihistamine which you have to take daily at night. if your symptoms still persist then your start using steroid nasal spray
, it has no side effect and it controls the allergy very well and you should start 2 weeks before your symptoms start. if this also does not cure you.
then get yourself tested for allergy, it is called skin prick test you will know what you are allergic to, then if possible you can avoid the allergen or you can start treatment called immunotherpy. this is currently the best treatment available and your symptoms will easily reduce by 80-90 percent kindly visit your ent specialist
he will guide you further.