Welcome to our Forum and congratulations on your practice of safe sex.  The activities you describe are no risk activities with respect to the most common STIs- gonorrhea, chlamydia and HIV.  For lesion diseases such as syphilis, herpes and HPV there is a theoretical risk for infection as these infections can be transmitted trough direct contact with lesions of the disease but I emphasize that these concerns, particularly for syphilis, are largely theoretical and should not be of concern to you unless a partner has a visible lesion..  As for HPV, nearly everyone (well over 80%) will acquire these infections and nearly but not all will be transmitted through penetrative sexual contact.  There are a tiny proportion of HPV infections which cannot be explained as a result of penetrative sexual contact.  You can nearly completely eliminate your risk for HPV if you get the HPV vaccine.

I hope these comments are helpful to you.  Please don't hesitate to use your up to two follow-up questions if any of what I've said is unclear or if there are further questions.  EWH