Me and my girlfriend have been trying to find her g-spot.. she's convinced she doesn't have one

Look, a lot of people are saying that g-spot is actually a myth. So, I think that your girlfriend and you should not be so concerned about this.

I believe that you both have this pressure when it comes to g-spot stimulation and you should not. She is convinced that she doesn't have one and then you are making a pressure in your heads. 

When you are having sex, instead of "mission" that you need to find it, you have to keep in your mind that you are having sex because you want to have it, not because something needs to happen.

So, don't be so focused on finding it...And I am sure that you will find it then.  GL

Sounds like yu found it alright. It is the rough-feeling place on the front upper inside of her vagina, kind of just "behind" her clitoris. It sort of feels like the roof of your mouth. This rough spot is meant to excite both her and you by stimulating the coronal ridge of your penis to bring you to orgasm so you can ejaculate your sperm inside her. But you can massage it by hand to lovely, intense effect, and likely bring her to orgasm from this alone. In concert with her clit and nipples etc., you should be able to get her there on a regular basis.

But remember, her orgasm is not just driven by her clit (or her nipples, her belly button, her anus, her mouth) or even her G-Spot. In short, the physical sensations you create with your fingers are only a PART of what goes into her orgasm. Most of it is actually in her head. The BRAIN, your MIND really drives your body when it comes to orgasms. The brain takes the sensations you create and mixes them with memories, fantasies, images and other stuff in her mind to begin the process that culminates in orgasm. A lot has been written about that, here and elsewhere, but it bears repeating. Orgasm is a delicate dance you do together (or with yourself). Lots of things go into making it happen, including strong feelings of love for a partner. Lots of things can also get in the way -- subconscious fear of punishment, thoughts of being "bad", etc., even desires for a particular, absent partner can distract you or detract from the pleasure you want and deserve. She may need to give herself  PERMISSION -- the freedom -- to have and enjoy the orgasm(s) you know she deserves.

So, keep exploring the sensations your bodies can create, and Good Luck!