Pigmen aggro'd for no reason

I entered the Nether for the first time in a while. As soon as i entered 5 or so Pigmen instantly attacked me and killed me. I have spent a lot of time in the nether and never had a pigmen attack me. when i respawned i ran back into the nether to get what i had dropped and a baby pigmen was still aggro'd (i have since found out about the aggro cool down, but the other adult pigmen was not interested in me?) When back in the overworld i had many items, netherrack quartz, bow, armour that i never even had. Strange.