My lil girl dropped probably about 34-35 weeks, I never felt a dropping feeling, but I suddenly stopped having back pain, had alot more pelvic pressure/cramping, and started waddling more. At my 36 week appt my midwife noted that her head is fully engaged in my pelvis so she's ready to go!! lol
Oh and walking will help a lot with allowing gravity to do it's job and bring baby down.
In first pregnancies the baby will drop usually around 35 -38 weeks. BUT remember that not EVERYONE experiences the baby dropping before labor. You will most likely know when it happens. But dont' be surprised if it doesn't happen at all. With the first baby that I actually went into labor with (first was an emer. c-section/no labor) the baby didn't drop til I was in labor. I remember with baby #4 he dropped in the middle of me gettign my epidural. I was sitting on the side of the bed and as they were inserting the epidural cath it felt like someone had dropped a bowling ball inside of me. He was crowning by the time they laid me back on the bed.
i felt my baby drop at 37 weeks. i didnt really have any breathing issues though so i didnt notice much difference. i just remember that day i was in the shower and i had this bit of sliding feeling inside and my doctor confirmed she dropped. im sure your baby will very soon!