Thanks for your query.Based on the facts that you have posted it appears that you have anxiety
about the length of your penis Have you measured the length of your penis in standing postilion,? The penis of a length of 3 to 4.5 inches is within normal physiological range.
Secondly the length of a flaccid penis has no significance it i the hardness of the penis on erection that is important as far as sexual satisfaction of a female partner is concerned.So you do not have to worry if you are getting hard erection.
Consult some qualified Sexologist
accompanig your partner for council ling and to allay her anxiety.