They say with first pregnancies it is normal for the head to engage (atleast partially) form 30 weeks on, it helps to stretch out the muscles and ligaments that have never been stretched b4, so that it isnt such a shock to them when the time comes. With second and beyond pregnancies it is common for the baby to move in and out of the engaged position because it is all stretched and anot as tight as with the first baby, and there for it isnt till the last weeks when its own weight and size catches it into place, with some second babies it is common for the baby not to engage till right before the birth, even as late as when the mother is in labour.
It sounds as though you are engaging, yay for you your breathing will become eaiser and you will feel lighter. Keep an eye on your weight, it has been noted that most pregnant women will lose 1 kg (2.2 pounds) in the days leading up to the birth!

Aww hun I had the same thing! I was workin and I felt pressure and I didnt know if baby dropped and some lady told me to go to the hospital right away cuz thats how she had premature labor so I got all scared and called my doc and went to see her and she told me its nothing really to worry about unless its followed by continuous lower backpain and pain across the abdomen. She said some women could even start feelin some sort of pressure at about 25 weeks! This happened to me like 4 weeks ago and sometimes every now and then I get a lil bit of pressure but the doc reassured me its okay hope I helped!

Shauna