How long does it take for trich to reaccur if you're exposed to it again? what do you do after that?

Depends: If the symptoms come back both you and your partner should be treated at the same time to prevent recurrence of trichomonas. As to how long it takes to come back-- it could very quickly within a day or two or within a week or two. It depends on the amount of exposure.

Trichomoniasis: Symptoms may occur within 5 to 28 days or much longer out. It might reoccur and be silent. If exposed again - get checked.