I've lost 24 pounds in 1.5 months and I haven't changed my diet or anything

That is not a good thing to lose so much weight in such a small amount of time, plus not even doing anything to do that.  I have never heard of anyone losing weight during pregnancy unless there was morning sickness and vomiting involved. How is your health right now?  Are you having any pain or discomfort at all?  How are your bowel movements?  I would recommend you see your primary physician to check you out to rule out anything serious like cancer or other health issues.  Let me know what your doctor finds out and what he/she will be doing for you.