Hey there, It's great that you don't want to pressurize your girlfriend and that you love her and care about her. I'm soon to be 17, and been with my boyfriend upcoming 2yrs.
I'll try my best to help and give some personal experience.
Not everyone is gonna move at the same pace when it comes anything revolving around sex. Regardless of how many girls you might meet have done so many stages earlier, not all girls are gonna be sexually mature and ready for everything at once.
The thing is guys tend to be more ahead of girls, and sometimes it can be other way round. But either way only the two of you can discuss these feelings together and you need to listen what "I'm not ready means" in her terms, they could be reasons she's resisting or she simply isn't in that stage yet to try oral.
But from experience I find the more my boyfriend tried it (not oral but certain things), and I wasn't ready - the more I was resistant to sex altogether because I ended up fearing if the subject would arise, however he would then claim "you don't love me" which I advice never give that impression if you truly love her - Just comfort her, reassure her and do not pressure the situation or subject, if she wants you to back off, do so. It doesn't mean anything bad on your side, and I know guys can take these rejections in the wrong terms, but genuinely its just the timing isn't right for the female and she needs to feel ready in herself.
I've gone through with things I let my boyfriend win over me, and its a very horrible feeling. Feeling like you have no choice or control in the matter, but obviously I'm manipulated and told things that aren't true, so in my position I try to make up to him but only feel bad in myself. (Unhealthy relationship I know)
But as you mentioned things are healthy between the two of you, you want to keep that balance instead of putting a weight load into the situation and things going into awkwardness and a messy relationship.
Just try relax a little, I know peer pressure doesn't help - but most girls would admire a guy who respects his girlfriends timings and listens to her side. You may hear these guys and girls going on about ALL the things they have done, but some girls just get this vague picture of what they have to meet up to, and not what some guys are actually really nice and straight forward about it.
You just really need to talk about it, and let her know its okay that's she's simply not ready, its frustrating yes, but is a little frustration worth having your girl or rushing and losing her? You never know what's around the corner if she becomes comfortable enough she might just surprise you aha. Try and out wait it
Sorry if not much help but - I tried!
x