Could be because fat cells do not like to lose their contents. They then grab a bunch of water to try to plump themselves up again. So you seem to gain.

Remember that sudden gains are almost always just water. Also you are very near a very low number - possibly less than ideal for your 5'5" height - so you aren't going to lose much more without starvation.

A rule of thumb is 100 pounds for the first 5 feet of height, then add 5 pounds per inch of height. For you, that's 125. Unless you are Asian/Oriental in heritage or incredibly tiny-boned, losing more may not be a good idea.

Don't get stuck with the number on the scale. It will take about 6 months after you get near your 'goal' for your body to reorganize itself. Be patient.

Gaining muscle while losing fat may make you heavier but smaller than you expect. So keep eating and don't worry about 2-5 pounds range of weights.