you clearly are allergic to something, and it looks like you are allergic to dust, may be even pollen.
you need to make a note if you sneeze when you go to garden or near plants .
also do you get sneezing
while cleaning your house or dusting pillows bed sheet mattress etc.
if this s troubling you a lot then you go to immunologist or allergy
he will do skin prick test on you, by this you will surely know what your allergic to.
once this is done you have to take immunotherapy
,this is the best modality of treatment available and it is very effective.
but before you try immunotherapy , you try nasal steroid
spray this also is very effective,consult immunologist or ent specialist
for nasal sprays.