First off, if you're working out with a trainer, shouldn't HE/SHE be able to help you with this?
Regardless, an hour and a half cardio 6 times a week is too much. Try doing a half hour a day of mixed HIIT instead (high intensity interval training). Basically, 15 minutes of doing...say...treadmill. Walk for 2 minutes, run for 1, up to 15. Same with say, rowing. Row at a moderate pace for 2 minutes, then push yourself for 1, up to 15. That will challenge the body much more than just doing 90 minutes at the same pace.
Diet, diet and diet. What is your current diet like? Avoid anything "white". White sugar, white bread, white rice. Make sure you're getting whole wheat/grains, make sure there is NO High Fructose Corn Syrup in anything you buy (it's literally in almost everything, so you have to shop wisely). Make sure you're getting plenty of whole veggies, enough protein and fiber to keep yourself feeling full which helps to stave off the urge to snack. If you want to snack, keep almonds or very dark chocolate around. Not in huge amounts, but small amounts are "good" for you, but also high in calories, so watch the serving size.
The site has some great diet plans that you might want to check out, as well as a multitude of other informational articles, use your resources!
And, don't forget to have fun.