Is there a week limit to sleeping on your belly?

Im13 weeks and the only way I can comfortably sleep is on my belly. I'm pretty slim and I've always slept that way. I've heard  you can sleep on your belly till it becomes uncomfortable, and I've also heard you should stop in the second trimester. Since I'm coming right up on that second trimester I'm looking for some insight. I've attached a picture so you can see my size. 

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