Something no one in their right mind would ever want to do with Nancy Pelosi. Or Hunny Bunny
Google it is the best thing you can do as your see pictures then how it's done rather than me trying to explain and confuse you.
Another position you can try is cowgirl or reverse cowgirl where she is on top either facing you or with her back to you then she is in control on how deep you enter her.
I did a quick Google search for penis depth guide and there are a couple products you can get how well they work is a different matter though.
I would say when your with her try googling sex positions then both of you look through and find ones you can try together, never be scared to experiment but take things slow until you know it's not going to cause her pain. How old is your girlfriend and does she have much experience?
the other person explains in his text to you.
Anything that involves straight on rear entry would be out the question except for spooning.
Another position is simular to missionary where your on top but instead of her legs being open and you between them she has hers partly together and yours are apart either side of hers and you enter her like that, that position will restrict the depth you enter her a bit.
Has she ever tried kneeling over you while your laying down and guiding your penis into her so she is in control in cowgirl position?
Even if you was to use a lubricant that had a numbing effect it still wouldn't stop her being in pain once it's effect worked off, I'm sure you have either knocked, squashed or even been hit it the balls before and know how painful that is and how long the pain can last well it's the same for a female when her ovaries get knocked during rough sex or he your big and get over excited.
njoynlife is the name of the other member who left the comment I was just curious to what he ment lol.
As I said a good sex life is down to good communication between you both just like if you don't tell her what feels good and what doesn't she won't know just like you don't if she won't tell you.
It's hard to know what more to suggest with only being able to know your side of the problem, would she be willing to talk to me on here so I could find out her side of what's causing her pain?