Olivia,

My daughter Olivia was like this as a baby, until I "broke" her habit of waking after 40 mins.....I tried all sorts, but the trick that worked for us was the CD player on repeat with a CD that is longer than 45 mins and has no breaks between tracks.........

PeaceBaby worked for us.....it has some special 60 beats per minute rhythm which is supposed to replicate the womb/breathing, so works well for babies to sleep to....

Maybe worth a try......?

(Olivia, and my son Charlie, and my new baby girl Lexie all have mini CD players in their rooms with this CD playing on repeat all day and night, LOL, and all 3 are great sleepers.....)