Nuvaring advice(possibly tmi so beware)

I just started nuvaring about a week ago and overall I like it a lot. I was on the pill and we found out that the meds I am on for migraines render the pill ineffective for birth control, so we needed to find a non-oral option for medication. My obgyn told me the two main options were patch or nuvaring since I didn't like the permanence of the implant. 
My question is, is it possible for nuvaring to be too large(or I guess for a person to be too small). I insert it up as high as it will go, but it always seems to sit right at my opening. I know the exact placement doesn't exactly matter for effectiveness, but I'm worried it will fall out. 

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