Well, if you've lost a couple of pounds in the past couple of weeks, you aren't at a plateau! You've been losing, just slowly. Trust me, slowly is great, even if we always wish the scale would move faster. If the scale is, overtime, moving in a downward direction, then that's exactly what we want to see.
A number of factors can effect the scale -- remember that the scale weighs fat, muscle, bone, skin, hair... all of us. When we talk about weight loss, we really mean we want to lose fat, but if you are retaining water, you might not "see" the fat loss.
Patience is really important -- this is a LONG journey. If you are sure of your calorie intake and keep losing slowly, that can be okay for your body -- although it can get disheartening to lose slowly. Changing up your exercise routine helps keep you from being bored, and upping intensity burns more calories.
I'd advise patience and sensibility! Sounds like you're doing great, and being under 300 IS something to celebrate!!!!!!