I was granted a multiple-entry Schengen visa area for a duration of 45 days. It is valid from 30/03/2018 to 01/09/2018. I visited Spain for 3 days (30/03/2018 - 01/04/2018). I have a trip planned to Italy at the beginning of August, which I was told not to put on my original application: the trip had a longer duration (10 days) than my Spain trip (3 days), which would be coming up first, and since they were more than 3 months apart I couldn't apply to the Italian embassy.
Is my visa still valid? It is still within the validity dates, but does the 45-day duration granted count from the first entry? Would it have expired mid-May regardless of how long I was in the Schengen area? This is my understanding and so I am applying for another visa for Italy. Will I have issues since it was a multiple-entry visa that is still valid from an end date point of view?