I will say in a smaller district you have more ability to get these kinds of things through. My HD asked for me back years ago and I started getting more days or stipend over the years. At one point I negotiated directly and somehow ended up with a bigger stipend than him... (less days still)
As a third year teacher you've also stuck out the situation long enough that you have a viable resume to move on. That may be your only real option for pay increasing in some larger districts that have set stipend amounts. You might be able to ask for more days... but a lot of districts have been phasing those out.