NEED ANSWERS ABOUT NAT TYPE WITH FIXED WIRELESS INTERNET

I had fixed wireless internet installed about 3 months ago. My Xbox has been running on a moderate NAT type since it was installed, and now all of a sudden it has had nothing but a strict NAT type. Playing online is almost impossible. I don't understand why it all of a sudden changed? I've been reading the forums and have come to the conclusion that this is almost always the case with this type of internet, and I've also read that port forwarding will not work with the fixed internet. Is there any way to get my NAT type back to moderate at least?