The first question I'd like to ask you is why do you suspect you taste bad "down below"? Actually, my first question should be, what exactly do you mean by down below? I’m going to assume you’re talking about your vagina, but down below is vague enough that it could mean any of the delicious nether regions that we all too often denigrate to a single euphemism.
I ask why because I’m aware that the issue of how a woman’s vagina, and more precisely her vaginal fluids, taste is one of those topics that causes many people anxiety. Most of us are raised with negative messages about our bodies and about other people's bodies. And a lot of negativity is focused on those parts of the body that are deemed sexual, like the vulva, vagina, clitoris, and anus. Sex, we're told, is dirty. And the only way to do it "right" is to try to keep everything as clean as possible.
Add to this the fact that men receive little to no education about women's bodies, and you've got a recipe for a whole lot of anxiety about whether or not our genitals are going to be acceptable to people who may not have the same body parts. It's no surprise, for example, that so many young people pick up more than a few negative stereotypes about the taste and smell of a woman’s vagina (it’s “dirty”, it tastes like fish, etc...)
The good news is that most adults who enjoy a healthy sex life, and for whom part of that sex life is the, hopefully frequent, experience of going down on a woman, end up loving the taste and smell of their female partners. After all the smell and taste is one of arousal, desire...sex really. So for a lot of people it becomes a turn on, not a turn off.
But this doesn't happen over night, and you'll need to take some responsibility by interrogating your own beliefs about what your body "should" look like or taste like. You may have a partner who loves the way you taste, but if you can't relax and believe them, you won't be able to fully enjoy the sexual pleasure he wants to give you.
Every woman has a slightly different vaginal taste, and it is dependent on many things, including natural secretions, arousal fluid, sweat, diet, and certainly whether or not you have any sort of bacterial or yeast infections.
If you want to experiment with changing the way you taste there isn't much scientific guidance, but there's plenty of non-scientific talk on the subject. Reading through some of it one finds an agreement that diet matters. Some of the foods that impact vaginal taste include raw garlic, multivitamins, asparagus, pineapple.
You mentioned reading that parsley, alfalfa and wheat germ will make you “taste better” but the fact is that taste is largely subjective, so while they may change the way you taste, the “better” part is really a judgment by you and/or anyone else you’re sharing your vaginal taste with!
I hope this helps a little bit. If you’re looking for more information on vaginal taste I can recommend visiting Violet Blue's Tiny Nibbles: Taste of a Woman and checking out this article about vaginal taste from MyVag.net