Like you, I had an anterior placenta in my second pregnancy, and my best advice, if everything else is OK, is not to worry about the fact that you feel less movement than you did last time. I had 2 single pregnancies, and the difference between the first, with placenta not at the front, and the second, with placenta on the front, was huge - so I can only imagine that it will be an even bigger difference for you, if your last was twins.
I felt a lot less, a lot later with the anterior placenta, and even at full term the movement was mainly round the sides, rather than those big all-over movements I had had the first time. Also my second was a smaller baby which I think affects it. I also think that as children they are different - my first is a tall, very active sporty child, and her little sister is much calmer and a more indoor sort of kid - and I have a theory that the difference was apparent even before birth!
All I mean to say is that all babies and all pregnancies are different, and with you the twins/single thing plus the anterior placenta is going to make a big difference.
Try not to worry - I know I did worry, and all it did was make the pregnancy less enjoyable.