My vagina itches a little bit inside but it comes and goes i had trichomoniasis last year but was treated for it. what could it be? is it stress?

Recheck, re-treat: Trichomoniasis, a protozoan infection, is transmitted sexually. It can recur if both partners are not treated simultaneously. Stress is more likely the result of your discomfort, but not the cause. Visit your local Planned Parenthood center for evaluation, treatment and discussion of follow through with your partner.

Hard to say: The only way to know for sure is to be checked.