New and looking for support

Hi everyone!
I'm new here and I'm loving it. I started using myfitnesspal three days ago and it's become my favorite app.
I'm a pretty active 32 year old woman who loves eating healthy, but suffers the bad side of being single: drinks!
So, my goal is to lose weight, going back down to 100 pounds, and keep it down in the most healthy way.
Every day I run at least 7km and I try to eat really healthy. Still I find it hard to keep a regular, steady, healthy, constant weight.
Any advice?
Thanks!