Queries :: Count Active Members Grouped By Month

I am trying to get active member count by month in MS Access.

Table looks like this:

admin ID firstName sDate eDate 1 Adam 01/01/2015 01/04/2015 2 Ben 01/02/2015 15/04/2015 3 Carl 01/02/2015 13/03/2015 4 Don 13/01/2015

Required output would be like this

2015-Jan: 2
2015-Feb: 4
2015-Mar: 3
2015-Apr: 3
2015-May:1
etc..

I got this far:
SELECT DISTINCT count(a.ID) as mCount, year(dimDate.Date) as [Year], month(dimDate.Date) as [Month]
FROM admin AS a INNER JOIN dimDate ON (dimDate.Date >= a.sDate AND dimDate.Date <= a.eDate) OR (dimDate.Date >= a.sDate AND dimDate.Date = null)
GROUP BY year(dimDate.Date), month(dimDate.Date)
ORDER BY year(dimDate.Date), month(dimDate.Date)

Query4 mCount Year Month 31 2015 1 71 2015 2 44 2015 3 13 2015 4