Safe to lose 2 pounds in a week?!

Safe to lose 2 pounds in a week?

Im 15 and wondering is it safe or ok to lose 2 pounds in less than a week? ive had some odd changes here lately and they wont go away. i had loss of appetite,nausia,headaches, cramps(never had before),(obviously weight loss),back ache and oddly enough my boobs have grown...Alot... Any ideas if this is normal ladies?i told my bf and hes just as clueless as me...

3 weeks ago
to awnser a question r asked, yes i am sexually active but that was a month ago(the last time i had sex) i doubt id be feeling anything like symptoms even if i was.

3 weeks ago
my period comes in about 2 weeks roughly...

i lose more than 2 lbs a week but gain it on the other week... but I'm physically perfect. i do also have loss of appetite(especially during breakfast and dinner), nausea, headaches, cramps, back aches and insomnia... but im ok.

you better have a check up... to be sure :)