I am on my third pregnancy where I have had to quit taking prenatal vitamins because of incredible morning sickness. My first two are fine, & I've every reason to assume this one will be as well. Since you can't eat a lot, concentrate on making every bite count. As best you can, stick to fresh produce and meats and whole grains. Getting your vitamins & minerals from your diet is much preferable to getting them from a pill.
When it comes to fruits & veggies, the general rule of thumb is the darker the color, the better for you is. It's not 100%, but it's an easy starting point. Baby spinach is reasonably mild, as are the small florets of broccoli (better yet, you can hide broccoli in just about anything), zucchini, that sort of thing. Blueberries are good, and if you cannot afford them fresh, look for frozen, unsweetened--I actually buy my blueberries & strawberries both frozen. I have always been able to tolerate cold stuff; you might want to try a smoothie made with a cup of frozen blueberries, a cup of plain yoghurt, and a packet of Stevia or a bit of honey. That will get you protein and vitamins. (You can also easily thaw the blueberries & mix 'em into the yoghurt & add your sweetener.)
If you don't like meat, you can get a good deal of protein from sources like nuts (buy them in the baking aisle & they'll wind up being cheaper than buying them in the snack aisle, and they'll be raw too so you don't have to worry about stuff like oil & salt. Canned beans are relatively cheap & convenient, as long as you don't think pork & beans is a good idea.
I'm fond of Old El Paso or Rosarita brand vegetarian (fat free) refried beans, some of those & some cheese on a tortilla & you've got a good breakfast taco. Brown rice & beans are a complete protein.
In general, don't worry yourself too much. If you were eating a reasonably healthy diet before you got pregnant, you (and your baby) will be just fine.