I have been sexually active and having sex with men completely pain free for 5 years or so. I recently has intercourse which started off well without any pain whatsoever, then randomly was feeling a sharp pain deep inside (near my cervix maybe??) And also felt some abdominal pain. I readjust because I thought it was the position I was in and was ok for a couple minutes of shallow sex, but as soon as it went deeper I was in so much pain again. I have had much more intense/deeper sex with this person prior and have NEVER had this happen to me. Other things to note: 1. it has been about two months since I had sex previous and 3. I am a menstrual cup user I have never had any pain using a menstrual cup and to my knowledge alway break the seal before removing so I am not thinking I caused any cervix damage within the past two months but I suppose I don't want to rule it out.
If this is a new partner it is possible he is just larger/different anatomy and is hitting your cervix during deeper penetration. Even without cervical irritation, hitting the cervix can be very painful/uncomfortable. There are a variety of different positions that cater to more shallow penetration and toys such as the OhNut can be beneficial as well.