How do you know if your skin rejects peircings?

I had got my lip pierced over 2 months ago. I was taking really good care of it,i washed the spot with anti bacterial soap,used neosporin and rinsed my mouth with mouth wash after every time i ate for the whole time i had it in(which was about a month) it was healing really really well,i still kept up with the routine of keeping it clean. Then one day it went full blown infected! It felt super sore and i looked at is and it was POURING out pus! It was sooo gross and it started to hurt really bad when i was trying to clean it and around the hole,there was these zit looking bumps that were all red and nasty looking. My lip got really badly sore,so i look it out and then next day the bumps were gone and my lip looks totally fine.

Around the same time i had got my ear pierced for the 3rd time and it ended up doing the same thing,minus the bumps. It was healing really good,i was taking care of it,the scar tissue lump was pretty much gone and it didn't have any more pus then randomly it swelled twice it's size and turned red and started hurting soooo bad!
So is my skin rejecting piercings? or is it something else?

-Thanks in advance for the advice ^^