I had protected sex on sep. 7th. we found ejaculation on the side of his zipper, and i'm not sure who's it is. i took plan b the next day. am i okay?

Yes. No. Yes.: Yes, protected sex is fine, especially if not wanting a baby, and especially if the protection is also against infections. No, it's not okay to say, "I'm not sure who's it is," when finding "ejaculation" on the side of one's husband's zipper. If it's not his, who would the extramarital person be? Yes, it's ok to take Plan B if one thinks primary protection failed (otherwise, Plan B isn't needed).