Back when we lived where it'd get really cold and our house was poorly insulated we used these for our windows & sliding glass door to help keep the chill out. All's you need is a hair dryer to shrink the film to the window and some sissors to cut the film to the window size.
Window Insulation Kit found at Walmart
Walmart also has things you can slide under your doors to help keep the drafts out too!

My kitties would also burrow themselves under fleece blankets if they got chilly, so having a few of those around could help too!

I have used the Window Insulation kits that BV said!  They work great!

I second having fleece blankets for your cat. We use them all the time in the hospital. You're right to be careful with the heating pads, they are just too likely to start a fire :S 

Gabapentin can affect body temperature in some animals so it's something you'll want to discuss with your vet. 

Skelletor : I have one coming it said same day and had great reviews (nothing below an 4star) pretty much poeple said it wasmt as warm as thye wish it was. Or there was a few areas with theres that seem cooler then other spots

amberellia and bv : were gonna try the srink wrap/ window instailler stuff tomorrow

Trig : the heatimg pads i have are for cats. Alot of people i talked to i  the group i was in for kittys with fhs uses them. I love the comapy i got them from. I just set them now] higher then settimg 2 if i am not around or going to bed the heated blanlet prob be on low settimg too for over night and were see how that goes 

this is the blanket i hopeimg still comes tonight it said same day https://smile.amazon.com/dp/B09MRSGT51?psc=1&ref=ppx_yo2ov_dt_b_product_details

for now i taped cardborad ( well as besr as i was able to tape didnt wanna stick to window. Theni tacked an flat sheet over that. They will have there heating pads on low tonight in there shelter boxs (ones people make to use for outdoor/feral kittys. But i made it for indoor use. There heating pads are in that. If power durimg winter goes out put blankets on top of thouse ;].

I actually have the window plastic on one of my windows all year round since it's a window that's very poor at keeping the air in and out, that's how well it works, me forgetting about it xD  I just remembered it last night, my kitten was messing with it o.O

Haha. The fuse blew again last night. I went around in my room and unplugged everything i wont need plugged in full time in hopes it will help. Only thinngs plugged in right now is the cable box , the tv is unpluugef cause if i need it that boots up quickly the cable box doesnt. The camrea in my room , then simba heating blanket which i gonna see if it will let me use up to the 2 setting. Phones can be charaged at the kicthen table i moved the power strip ober there cause it on an diffrent fuse. With my ipad i use back up batterys if it will let me. Just tryimg to figre out what needed vs not . This time i didnt think it blew because of me. But i unplugged anything i didnt need so we can havethe heater in my brothers room on. And hopefully i can have the heating blanket plugged in on an low setting