K.L.
When I was pregnant, I was considered "high risk" as I was diagnosed with partial placenta previa at 12 weeks along (i had some major bleeding), so it was very important for me to follow the rules that my OB set out for me. I was ALWAYS a stomach and back sleeper, and so went into specifics with my doctor about this (he is a high risk/infertility OB schooled at Stanford) and this is what he said: lay however you want including back, stomach, etc. until it is uncomfortable for you - your body will let you know what is an okay sleeping position and what is not. Since you are not far along at all, you are still safe sleeping in any position you wish as there is NO risk to your fetus because it is still completely within and protected by everything in your abdomen including organs and fat. I was able to sleep on my tummy until I was about 5 1/5 months pregnant (I was very small, though) and slept on my back until it became uncomfortable for me at the end of my 6th month.
Now, sleep however you are comfortable, especially with the morning sickness: I lost 15lbs my first trimester because I was SO ill with "all day" sickness - your body will let you know soon enough what is comfortable and what is not. This is the LAST thing you should be stressing about at this point - focus on trying to eat frequent and well balanced meals, despite the fact that you may be nauseaous all day and all night. You have to force yourself to eat and drink for the good of your baby - try to get as much sleep now as you can, as it will get harder and harder to sleep well the further along you become. Focus on keeping yourself and your body as healthy as possible, and dont sweat the small stuff like sleep positioning or the one cup of coffee you have a day.
Good luck!