You should definitely send a written enquiry into their plans and intentions over renewal of your contract. CC it into your bosses boss too, so it is not just ignored.
Not sure what type of work you are doing but start powering down as well. For instance, if a new task comes in that to complete would take longer than your contract allows, refuse to start it or make it clear that although you can make some plans and initial headway it will not be you completing it, so time for handover documentation would need to be allowed for etc.
Start looking for work anyway. Do not put all your eggs in one basket. When they approach you (if they do) you can then at least tell them you have other offers, and in fact job hunting can be fun too. Use recruitment services as they do a lot of the hard work and leg work for you.
Start booking time off for interviews. That normally puts the cat amongst the pigeons too. Book time off for an interview at one of their biggest competitors (even if you have to make it up), you do not have to give them any details, but it might jolt them a bit.
Definitely do not let it stand. You need to know. It is not desperate or needy and your deadline is looming. I would have started this process weeks ago.
Good luck with it.