why does the fuse for my ECU keep blowing?

There are so many reasons why this could be, but the easiest answer is that there is a short somewhere. The easiest way to short something in a car is rust/dirt/fluid build-up, but happens occasionally with the cigarette lighter -- if you're using a cheap adaptor for charging your phone, there might not be a fuse inside it. And obviously check to see if this problem stops after you don't use any accessories (including plug-ins like dashcams). Also check with your manual that all the fuses in your fusebox are of the appropriate rating. I bought my car used and found that somebody had used a 20A fuse instead of a 10A one (or something like that) and was the reason why my lights kept going out.