Not gained weight during 1st trimester of pregnancy?

before i got pregnant i consistently weighed 8 stone and 2 pounds for a couple of years, but after my first trimester ended at about 13 weeks i though i would be brave and get weighed for the first time since being pregnant to see how much weight i had put on, (i had also just read in a e-mail newsletter that said i should have gained about 5 pounds) on weighing myself i found that i was exactly 8 stone! so instead of gaining anywhere around 5 pounds i lost two, i don't eat very well havn't done for years, as i don't have a mive appetite. but i had been trying to eat a little more and better, but i just don't see where i should have lost the weight even though its only small while i should have been gaining it, i stayed 8 stone from when i got weighed at about 13 weeks up to about 15and a half weeks and i am now 17 weeks and i am back too 8 stone 2, but no more, my belly is getting bigger by the day, and has been doing since i was 11 weeks, (this is my first pregnancy) its still only a small bump but i now look "pregnant". i just wondered if any other mums to be are experiencing this, or have experienced it?? i mean, i'm sure the baby will be ok? because it will just take what it needs, i just find it a bit odd :S