I have killed two dragons recently; A frost and an Ancient, and did not absorb the soul of either.

I have 58/60 shouts unlocked, and need 2 more souls... very frustrating!

Any help?

You'll have to be more specific.

If you've killed those dragons before, like revisiting a word wall with a dragon, you won't get the soul again.

Well, they were at a word wall, but surely a dragon is a dragon and I can take its soul?

Easy enough; If you are on PC, type "player.modav dragonsouls 2" into the console.

I'm on an xbox dude, thanks anyway