The representatives and senators represent both voting and non-voting residents of their district. In fact, every member of Congress has a section of their office devoted to helping people they represent in their dealings with federal agencies, which mostly ends up helping people with immigration cases, and people with immigration cases are almost all non-citizens, who cannot vote for Congress. (If you go to your Congressman's website, there will likely be a section about contacting them for help with an immigration case.) Therefore, your members of Congress definitely represent you, and I would say you are their constituent. Though that depends on what you think the definition of "constituent" is -- whether it means a voter or someone who is represented.
In the decision for Evenwel v. Abbott (2016), the Supreme Court wrote:
Nonvoters have an important stake in many policy debates and in
receiving constituent services. By ensuring that each representative
is subject to requests and suggestions from the same number of
constituents, total-population apportionment promotes equitable and
which uses "constituent" in a way that includes non-voters.