It's old blood, don't worry!

but why all the sudden would this happen ? ive never been to the gyno before either so it worries me

You should schedule something with a gyno now that you're sexually active.

Brown discharge can be from a number of things, I had assumed since it was a week after your period that it was just old blood finding it's way out and I still think that's what it is, unless of course you have other symptoms.

Who knows? Did you get a little irritated from sex last night? This blood could be from anything and unless you get more symptoms, I'd say you're fine.