Well there are a lot of things it could be and without seeing your exact foods list I really can't tell. Here are some possibilities though:
1. You've hit a minor stall point.
It's not really considered a full 'stall' unless you haven't lost anything (weight or inches anywhere) in 4 weeks. Each of us have minor stall points where our bodies seem to resist changing. Once beyond that point though, the weight/size loss kicks back in fervently (at least for me it did, and mine was the 180-170 range also).
2. You've replaced the breads/pasta with something similar in nutritional makeup.
Are you eating more potatoes? Rice? Corn & carrots? Bananas? Each of these is also rather high in carbs for its nutritional content and while I'm not saying these are unhealthy things, there are definitely alternatives out there with lower carb content.
3. The scale lies.
Even the most well-made scale cannot account for things like TOM bloating, forgetting to urinate before weighing, and various things like that...and the cheaper scales will readjust the weight they display simply by how you step on them.
I make a point to weigh myself at the same time and in the same circumstance every morning (ie naked just after I wake and potty but before I shower).
While I have been weighing myself daily I do not "count" it (in my head or in my tracker either one) unless it is on my official weigh day, which for me is every 10 days.
In addition, I -always- measure myself on my official weigh days, because even when I wasn't losing weight I was losing inches - and this helps me keep from getting discouraged during a minor stall.
4. It's TOM for you?
Always a possibility with a female. When it's my TOM I try to avoid the scales as much as possible.
5. You aren't drinking enough water.
Insufficient amounts of water can cause you to stall or even gain instead of lose (bloating).
There are other things it -could- be, but those are the most common ones I've seen.