The other day over on the Yoga Forum, someone mentioned that sitting in meditation was uncomfortable for them. This is often the case - at least for me. My legs will start to go numb after a while, and when I first starting meditating regularly I found it really difficult to sit up straight for an extended period of time. While sitting up straight is now easier for me, my legs still do go numb. My yoga teacher always said to just ignore it - that it wasn't a bad thing and that eventually the meditation would be over and your legs would be fine, haha. So you could suffer through it, or you could try one of these four ways and see if one of them feels better than the way you're currently sitting.
For these seated positions, I used a couple of props: a manduka bolster, two foam blocks (I normally recommend cork blocks for practice but for meditation the cushion of the foam is nice), and of course a yoga mat.
Give these a try and let me know how it goes!