I don't follow what you mean or what you are getting at, you have to expand on your question..

Could you get an std from a piercing that is infected? My boyfriend has a piercing down there.

With open wounds there is more of a chance for the infection to cross the barriers and infect the next person.

He didnt have anything before he got his piercing and he has only been with me, I was clean before too. But now we both have chlaymdia.

No, you have to get a STD from someone who has a STD.

If you both tested before you started having sex and both were negative then this is a new infection picked up from someone going outside of your relationship.

what made you and him test?

It was time for my yearly exam and it came up. We are waiting for the results of his.