Do you have a partner who is concerned about her size and feeling a little self conscious about being at the helm of the action?  Here are some things to consider:

1. Being on display while fucking you.  You may want to show her there are other positions that she can enjoy your ass in.  For instance, you can ride her girlcock…this puts the onus on you to be the active one.  Another is to have you on bent over the side of the bed and she can stand behind.  These may help ease her into it until she finds her confidence.

Pegging Positions
2. Strapons not fitting. - I am not sure of her size but if this is a concern, there are several plus size strapons that will adjust to fit any body size.  Here are a few:

Plus-Sized Strapons

Other than that, just encourage her to play with your ass more…perhaps she can manually fuck it with a dildo to see how hot it gets you!