My friend, 6.5 lbs in 5 weeks is BLOODY BRILLIANT WELL DONE!!! :clap::clap::clap:
The new WW diet focuses on making you lose FAT rather than muscles, which comes off quicker. Losing fat is a slow process, if you don't lose at the same time water and muscles, but in the ending line you will see the difference, you won't be as flaccid as you would have been if you had lost muscles as well as fat, and your resting metabolic rate (BMR) will be higher, which means you WILL be able to MAINTAIN your loss better.
What does it mean that you had your first period in 2 years? Remember that when you have TOTM you retain water, so your "STS" this week could mean that actually you have lost and you will see a great loss next week!
A big hug, don't give up you would spoil all the hard work you've made in the last few weeks!