Try Jane Clarke's (a Nutritionist) Bodyfoods cookbook for a bit of inspiration and advice. Foods that give a steady release of energy tend to be carbohydrate based wrapped up with a bit of fibre so as your body breaks down the fibre it releases the energy. Oatmeal is very good as its fibre is water soluble and dried fruits are a good base for snacks as they give sugar without the instant high followed by the low that instant sugar sources give you.
I found if I got even slightly constipated, as you do in all the time in pregnancy, then I got awful headaches that went on for days. I have tried to be as nonchalant as possible in taking the fybogel and carrying a bottle of water rather then reaching for a can of diet coke helps.
You can snack on things like flapjacks with apricots, cheese with oatcake and an apple, a yogurt and banana, bowl of cereal or janh's peanut butter on toast. (There are some people who are advised to avoid peanut butter when pg ie if you have a history of nut allergies in your family but I think in the overall population they are quite rare still. I'm 10 weeks further into my second pg and would rather eat something I fancied occasionally then get paranoid and think about it the whole time.)
If you have lemon squeezer and a blender or one of those stick mixers you can make yourself smoothie style drinks without needing a juicer. You can use a banana as the base and then pop whatever fruit is around in the bowl, rougly chopped, skin on, and add some yogurt, orange juice from a carton, and sprinkling of porridge oats and a bit of root ginger for interest and whizz it all up.
Are you iron levels alright aswell? Hope you are feeling a bit perkier soon. Do be nice to yourself.