At Last! A gal who freely admits she is no Annie Oakley in the saddle, though one who likes making puns.
Most guys will be fine with it – a little disappointed, perhaps, at the lack of variety, but it is no dealbreaker. The problem is you will be a little disappointed too. You already are or you’d not have asked about it.
Sex is like everything else, the more you practice, the better you get. In your particular case, make a game of it.
Try a Dom Cowgirl at first – like a regular Cowgirl, except he is not allowed to move from the waist down at all and you control the pace completely. When he starts moving, and he most definitely will after a bit, roll over into your preferred position. You’ll find you’ll be matching rhythms for longer and longer before you need to roll over.
Stop worrying about it. Slip-outs happen all the time in the heat of the moment, they are no big deal.
Sex is meant to be fun for you both. Spending precious time worrying when you should be tuning your body to his is no way to run a rodeo.