a week isn't long enough to see results, especially at your size. if you weigh 138lbs, you will see numbers from 133-143 on the scale without you having gained or lost an ounce. it's all normal variation in your weight due to different amounts of food, water and waste that happen to be in you at the moment.
you're at the point where you really do need six weeks to see what happens. because you aren't big enough to have 2lb per week losses. a pound a week is pretty aggressive for your size and activity level. so you're realistically looking at a half a pound a week or less in loss. again, when you don't have much to lose it comes off slowly.
but look at that half pound a week compared to just half of normal fluctuations, which would be 5lbs. it's a tenth of it. that's why even if you do everything right and are losing you may not see that half pound loss on the scale, even when you are losing it. it's why you have to wait for all those little losses to add up enough so that you can see them.
i mean, if you're female and you timed the weigh ins for the right week, that gain at 1500 has more to do with water weight gain during your cycle than anything you ate. that's why some people don't weigh that week.
-google first. ask questions later.