Should I/How to tell me therapist about these things?

I've been seeing my therapist for about 4-5 months now about my anxiety. I've gotten so much better to the point where we were planning on finishing in 4 weeks time (we are spacing out meetings so I have 2 meetings left).

But recently I think I've stared to identify bad things in terms of eating... lowering my calorie intake by a bit, obesessively counting calories, I keep increasing my excersize and trying to loose weight even though my BMI is "underweight". I just want to be thinner. Like, I don't look skinny. I look the same as I did at a much nearer to "healthy" BMI. I don't want to be all skin and bones but I just want to lose more weight and I've been doing this for a while now. And it wasn't so bad before but I think something must have triggered me to suddenly go into this obsessive state over the last month or so and I can't stop thinking about what I should do to keep loosing weight, like I will be in class or in the toilet or talking to friends and suddenly I'll think "how many calories have I eaten today? How much excersize do I need to do to loose more weight?" every other minute of every day. I also seem to be getting increasingly emotional whenever I feel like I've gained weight...

When I put it like that it sounds like I should tell my therapist... but at the same time, like... I still eat 1000 calories a day and I still have my period and I don't take laxatives and don't think I'm fat or anything, just a little chubby, especially around my belly area. So I'm sure I don't have annorexia or anything.

I don't even know if it's worth mentioning...

And every time I think about telling her, I just don't know how. How do I bring it up? How do I talk about it without making it sound like I'm overexaggerating things? Is it even worth mentioning? What if she thinks I'm lying? She won't force me to start eating more, right?

Well some of those thoughts sound a bit obsessive. So one way to introduce it to your therapist is to say hey, I have been having some obsessive thoughts regarding my calorie intake. That will probably be enough for the therapist to probe. And the therapist won't think you are exaggerating, you are providing your perspective.