I agree that your first dream reflects concerns about moving in with your boyfriend, which, as you indicate, were weighing on your mind. In the dream you three are "moving in and out of buildings" together, an allusion to your housing dilemma, when suddenly you arrive on the roof of a building. Because the roof is an elevated position, and a location of perspective, the operation of your higher self is alluded to by the dream. (The roof may also be a reference to the "high" you were feeling at the start of your new relationship.)
Nevertheless, concerns about reaching the ground level, that is, grounding your relationship, already are on your mind, most likely due to consideration of how your son will fare in the new equation. Your boyfriend underestimates the work required to reach this ground level. He begins jumping between floors (skipping steps), and sure enough, the dream soon represents your deepest fears. Your son, naively following your boyfriend's lead, plummets to his death. It is significant that your boyfriend does not appear in the dream to rescue your son.
I am often asked if dreams are precognitive. The best answer I can give is that they frequently are, but only in the sense that they show us things that we already know at a subconscious level. Your dream report indicates that the early doubts which you held for this relationship still linger. And who could say that you haven't known these doubts all along?
Your second dream, though equally frightening, actually employs a fairly comic device of dream communication. In the halls of the legislature building -- an allusion to structure and stability -- a wild horse is loose and bearing down upon you. You press repeatedly upon a door calling for your son to let you in, but he merely replies "I'm changing," and the door remains shut. You presume your son is changing clothes, but a more literal interpretation of his words might yield a truer interpretation of their meaning. Your son, indeed, is changing -- both physically and mentally. Might I suggest that the dark horse represents the heated engine of adolescence, and that the closed door signifies the end of one era -- his boyhood -- and the beginning of another -- his young manhood?
In another e-mail you wrote to me that you have raised your son from birth as a single parent, and that you have a very close relationship, of which you are very proud. Your son is a fortunate child. Your love will forever be reflected in his life.