I keep seeing your question and hoped someone currently doing Momentum would respond. Since that hasn't happened...I am very experienced with Momentum/Flex but have been following a sort of modified PP program since PP came out but do still remember Momentum.
Anyway, back when I was doing Momentum I recorded calories and 1 Point for me equated about 48 calories which is 1008 calories (and that included the zero point vegetables I was eating).
So if you are eating somewhere around 1000 calories a day then I don't think it should be possible for you to not be losing particularly with your level of activity. I tend to lose slowly. I'm at a similar weight as you (inch shorter) and I record my calories. I'm averaging eating between 1150 and 1200 calories a day. I'm not as active as you but I am still losing although only about .6 to .7 pounds a week.
Exercise can cause some water retention but that wouldn't continue long term.
I have to wonder if you are correctly calculating your points. This could be from getting the portions wrong or from using a calculator that isn't correct.
Are you using a calculator that you had from before or are you using a calculator found online?
Do you weigh your food? How do you determine how much you are eating for purposes of calculating points?
Have you tried counting calories? I find that counting calories has really been invaluable to me at times.
I just have to feel that if you aren't losing at all that something is going wrong in the point calculation end.
On reasons for not losing I found this article helpful to me (some of it is PP related but you can ignore those parts as most of it would apply to anyway who isn't losing, regardless of plan)