Internet being really slow

[Garrison Marsh]

So a few weeks ago I was having this problem and i came to the conclusion that the door being closed in the room with my router was causing it to slow down. And even though it did cause it to slow down a bit, i know now that that isn't the real problem. Our old router (which was the exact same one that we have now it just died) worked great. But it seems like since we have gotten out new router the internet has been very strange. Right now the speeds are fine but it is very inconsistant on all of my devices. Right now my speeds are about 30mbps down and 6 up with 54ms latency but last night when i tested it the up and down was about the same but the latency changed every time i did a speed test, it would go from 30ms to 200ms to 80ms for each test. As you can guess gaming is a nightmare like this. I don't know what the problem is, i am thinking is could be the router's fault since it seems to have gotten bad since the new router but would it be worth contacting my ISP? Also i have done these tests on my phone, PC, laptop, and my dad's macbook and the speeds have been the same.