Soft brick help!!

I've had my nexus 5 for awhile now and decided that I should try to root it. So I followed a guide and youtube and it worked. I then followed a guide to install the android M developer preview, just to check out what had changed. From there I decided to install Cyanogenmod 12.1 . So I was looking at this guide when all of a sudden i noticed my root was gone for some reason. (im new to all this, not sure if that was supposed to happen). So then I followed the same rooting steps I used for the first youtube guide I watched. everything seemed to go fine until i realized that i was in a boot loop. I then decided to go ahead and install Cyanogenmod 12.1 anyway. It worked and my phone was fine. Until i woke up this morning and saw that it was in a boot loop again, but now I can't even get into my custom recovery (TWRP). I dowloaded this program to completely return my phone to stock but every time it tries to flash something to my phone, it gets this "flash write failure" message. Now I'm really lost and do not know what to do. I really rather not buy a new phone.

If anyone can help it would be really appreciated!!! If you do, I will need you to assume I do not know anything, as I'm not very familiar with everything.