HELPP!! Let downs when you're not nursing?!?

I've had 2 kids before and am pregnant with my 3rd, and I am a bit anxious because both of my nursing relationships I have had letdowns when I'm not even nursing, and I end up with the whole front of my shirt soaking wet! Even while wearing "heavy milk pads!" I've tried everything it seems, even lillypadz brand sillicone they're supposed to keep you from letting down but it hasn't helped much, has anyone used the "milk savers" silicone cover? I'd like to hear what you've done to help solve this...I can't bring my pump everywhere, and my baby can't be latched on 24/7 :(