I'm having trouble breathing after going up stairs and easy exercise and its been getting worse, is it bad?

also i have been diagnosed with asthma before but have not had a major problem since i was 13. It started recently a few days ago and every time i walk to the train station (which you have to walk a short uphill sidewalk from where i live) i cant breath afterwords and i have to sit down or kneel or it hurts, and it still hurts when sitting but it eases it more at least. I don't know if to go to the hospital because after a few minutes it does go a way with rest but the recovery time of feeling better has gotten longer. So i don't know if its my imagination or its a threat to me.