Same here--basically a couple of years ago, I had a medical emergency that required me to be on a nasty anti-inflammatory steroid for 6 months. Besides the the other literally life-changing side effects (stretch marks, shrunken testicles, developing breast tissue) it kept me up every night. Luckily, my state had just legalized marijuana, and I had been using that as a sleep aid since, since it knocks me the fuck out.
The flip side is, I now can't sleep without it, and while I've been meaning to to quit it, I'm only doing so because of the unfortunate fact that I'm now flat broke--un-employement dried up, and my tax return is three weeks late, so I've been up for most of the week.
All I can suggest in your own predicament is to have a serious discussion with your girlfriend about each of your sleeping preferences, and fankly it's not un-heard of for couples to have differing styles, if not sleep in completely separate beds. Depending on how she reacts is probably a good indicator of your potential relationship.
Anyways, LC is post.