It sounds like you need to expand the resources you're using. You need to learn more than just vocabulary and start learning GRAMMAR. Verbs, adjectives, particles, everything! Teaching yourself is a pretty crappy way to do things, but if you don't have an alternative, you might do well by checking out these sites:
Tae Kim's Japanese guide to Japanese grammar
Tad Perry's Quick and Dirty Guide to Japanese
If you've been studying for seven months and still don't know how to describe nouns you must be doing things wrong.