im frustated,i lost 7 pounds in 3 weeks,now 5 weeks down the line i have lost inchs but gained weight, will i ever lose weight and when??

i go to gym and do spinning classes 5x a week,dont eat junk,eat about1500-1600cals a day,ive got 6 kids so im not lazy, i bought a hr monitor to see how many cals i burn a day,some days i burn 3404 a day when i do alot ans about 2,896 when i do nothing, i eat way perfectly healthy and no weight loss, i am feeling bad and wanna giv up the gym, i am glad to lose inch but i wanna lose weight too, i am 11st 7lbs and 5ft 1, i was 12 stone end of dec 07

please help