1. The uterus can "point" in different directions. The cervix is just the opening of the uterus so it can point up or down a bit or simply straight forward. When hit from the "wrong position" some women just experience pain. The cervix sometimes can be hit and there is pain and sometimes it can be hit and there is no pain.
The vagina is like the penis it comes in different depths. So ladies with "less" depth to their vagina may experience more pain on deep penetration just because of anatomical limitation.
New onset pain with penetration can be a sign of infection. This would tend to occur with any type of penetration whether "deep or normal"
2. Historically regular "KY" jelly original (white is water based) was created for use with medical equipment, not sex. For sex it may be better for most people to use lubrications that are created for sex. These are water based which do not damage condoms. Any oils including baby oil should not be used for sex. They deteriorate condoms. This can lead to all the things condoms are used to prevent: transmission of sexually transmitted infections and pregnancy. Also, oil and water does not mix so you can harbor remnants of oil inside the vagina or rectum helping increasing chances increasing irritation of the vagina or rectum. Just think of it this way. If you spill cooking oil (or any oil) on you skin how long you have to wash to get it off. Now imagine that is your sensitive areas. That's a lot of soap and a lot of "scrubbing".