Anti-Lock light flashing a code....

Hey all, got another question for you that have maybe had the same thing happen or just now what it means...lol Today I was driving in town, went to stop at a stop light and the Anti-lock brake light started flashing what looked like a code...flashed (13)times I think it was and then solid burn. I had a to go to HD and when I started the truck to leave the light was no longer flashing or burning, untill the first stop light. I still had some running to do, so I tried to pay attention to it. I did notice I blew a fuse for turn signals and such (pulled trailer last night and plug came apart when I unplugged it) so I replaced the fuse thinking maybe it had something to do with the light.
On the way home it did not burn again untill the brakes were applied, but I did notice that a light braking did not turn it on. The light only came on when the brakes were applied with some pressure, nothing real hard but more than a feather touch. Light goes out every time when the truck is shut off untill that first stop, then burns untill key is shut off.
If anyone knows if it a sensor or what, I would appreciate it so i can fix it!! thanks