Calculation to get remediated value using month differences

Hi,

I am looking to be abel to caluclate the below month on month using DAX

((July Total Vulns + Aug New Vulns) - Aug Total Vulns) = Aug Remediations

I have a file that takes a load in at the start of each month (LoadDate) 

I then check to see if this [Vulnerabilitity ID] is new or was present in the previous month using the following calculation  which will mark it as new or old. 

New at LoadDate = if
(CALCULATE(COUNTROWS('Rapid 7 Sample'),FILTER('Rapid 7 Sample','Rapid 7 Sample'[Vulnerability ID] = EARLIER('Rapid 7 Sample'[Vulnerability ID])
&& ('Rapid 7 Sample'[LoadDate])=EARLIER('Rapid 7 Sample'[Last date of previous month])))>0,"Old","New")

I need to calculate the below but have it ongoing month on month 

Total Vulns = Old + New for that month

i.e. in Feb  --- ((Jan Total Vulns + Feb New Vulns) - Feb Total Vulns) = Feb Remediations

i.e. in Mar  --- ((Feb Total Vulns + Mar New Vulns) - Mar Total Vulns) = Mar Remediations

((Month -1 Total Vulns + Month New Vulns) - Month Total Vulns) = Month Remediations

Any help or guidance would be greatly appricated. Thanks!!