Trichomonas is a STD that does not give symptoms that you have it for sometimes long periods of time. Yes, possibly even a year. This is a parasite. Some men do not have any idea that they are carriers of the parasite and many women are clueless until they have a vaginal discharge with a bad odor and itching. A simple urine test will reveal if you have Trich or not. Treatment is simple, flagyl (an antibiotic) will take care of this but only if both partners are treated at the same time.
Yes, and they can keep giving it back to you even if they are faithful. If they are not, there's your answer. You must both be treated at the same time and abstain for however long the dr says