Lord I hope you gain some weight back! You're essentially my size pre-baby. I just lost 12 pounds after a tonsillectomy and got down to 116. I looked like death warmed over! So you're at what, like 107?? I honestly cannot believe you are still producing any milk. Or at least any milk with any fat in it. You're baby is gaining weight and everything? After my 3rd, I lost all the weight very quickly, but I was diagnosed with a thyroid problem when she was about 6 months old. She had gone from a chubby 50th percentile baby to a scrawney 3rd percentile baby from her 4 to 6 month well visit. I had been exclusively BFing until then, but right away I started her on some solids and changed my diet entirely. I added in a TON of good fats, started doing protein shakes every day, and found recipes to increase fat in my milk. Worked like a charm. Of course, I also gained about 5 pounds back.
Here's my point: I've breastfed 3 kids successfully for over a year each. And I have NEVER lost the kind of weight you are talking about (nor have I known any of my friends to experience this). In fact, I usually hold on to a few pounds of the post baby weight and then drop it as soon as I have weaned. If you are eating correctly, I don't see how losing 45 pounds is possible. Now, I know every "body" is different, but it sounds like you are not doing this very heathily and it could have devastating effects on your body long term (ie, bone loss, hormone regulation). Oh yeah, forgot to mention I'm a registered nurse and a fitness instructor.
My guess is that, yes, once you wean your baby you will definitely put weight back on...and that is a GOOD thing!