Secret fit belly is so awesome and really comfortable. I had two pairs of jeans from Mimi with that belly and they were my favorite and most comfortable pants - I wore them until the very end and post partum too. With not much belly post partum, they stayed up pretty good, but still fell down a little. It helps them stay up if the jeans/pants part fit you a little snugly or just right. If they are too loose, they will fall down.
I also did not have much luck with the bella band - it doesn't stay in place and you end up looking a little lumpy with pants underneath. You need a top that covers all that to look decent. But, I recall my pants still falling down. For the early stages I found a pair of jeans at the Gap that had the roll top that rolled down over my hips and fit really good. Once you get a belly though, these are not comfortable as they cut into your lower belly. I got them on clearance last january - this is the best time to shop for clothes on sale!! Frankly though, at some point or another, ALL your maternity pants fall down, I found no perfect solution. There are some little suspenders I have seen that clip to your bra and your pants that are supposed to help, but I never tried them. Good luck and congrats!