Even if there is slight unprotected penetration involved,, and crown of the member comes in contact with mucus membrane of anus, the risk is there,,, for both. Though it is not high but not zero either.
There is a strong possibility that your partner may not be a +ve. What I suggest, get a p24 duo test done after 4 weeks of exposure, which will be highly reassuring and give you peace of mind. This need to be confirmed by a 3 month AB test.
just slide in about 1 or 2 cm then i push him away from me
there was no penetration?