Interesting dream. Mind if I share some of my thoughts?
Of course, being generated from your mind, only you can say whether my thoughts are accurate or not. So, the interpretation I am about to give is probably going to be somewhat off the mark. Here it is.
There are two main events and two main circumstances. The events are 1. being pushed into the girl you like, and 2. choosing the correct Host. The circumstances are 1. the communion line, and 2. needing to make a choice between two Hosts (ie, no Hosts left in Chalice, two unknowns on the Altar).
Im guessing that youve recently been considering the question of how to know what is true and how to know how to make the right choice, as well as considering, in light of the first question, how much one is culpable for, or guilty of. Am I right?
Being in the communion line seems to represent your approach to a decision. The priest seems to be a conscience figure, emphasized by his look (which I presume is a look that is supposed to make you feel bad for something you did wrong). Thus, on the one hand, it seems that you dont really feel like you deserve to be guilty for some of your wrongs (the wrongs being symbolized by the nature of your relationship (you being attracted to her, but perhaps you are afraid to let her know?) with the girl you like). I say this because you didnt choose to bump into her, you were pushed. Pushed by what? Something so familiar to you (your natural urges) that it is symbolized by a friend (who also happens to be female, again symbolizing your natural desire to be with the one you are attracted to). So, on the other hand, while you feel you were pushed into you, you still feel guilty for it, your conscience tells you its wrong (the priest and his look).
This is one thing that can happen when you approach a decision, and in fact, no decision was actually made, you were driven (in this case pushed) to do something wrong, rather than actually choosing it.
The second thing that happens is when you actually do make you own choice. The priest, the conscience who tells you what youve done wrong, but also guides you to the good, exclaims The Body of Christ, and you assent to that truth in word: Amen.
Thus, here, the Body of Christ, the Host, is a symbol of what is good and right and choice-worthy. Yet, what is good and choice-worthy isnt always clear, thus you are faced with the dilemma of the two Hosts.
Moreover, merely saying that it is true, assenting to the truth in word alone is not enough, you must actively choose it, and take it, which is why your conscience alone could you provide you with what is good and right and choice-worthy, it merely guides you to it. Now, it is up to you to discern what you know is true and right and good, from the lie. Moreover, you must choose it, not merely assert it.
It seems that you feel that in the end, you will choose the right, that even though you sometimes get pushed into doing things you dont really want, in the end, you really do want to choose the good. Moreover, you also feel that, even though you may not be able to discern what is true and good with absolute certainty by the light of reason (symbolized by your vision, two hosts, one big one small, which one is the real one? I know the big one was consecrated during the consecration, but do I really know it for sure?), you seem to believe that your sense of touch (symbolizing what you feel in your heart) will affirm what your sight (reason) told you was true.
So your dreams seems to be about the dilemma you face daily in working out what is good for you to do, and how to know it. It contrasts what you often do in your failings with what you do when it really counts. You seem to feel that you never really choose the wrong, but do still feel guilty for doing it. But, you also seem to feel that when you do have make your choices, your heart and mind, and conscience, will help you make the right decision.