Short Banjo String - Will Stretching Help?

My girlfriend and I have been together for 2 months now, and sometimes when I go over to her house we sit on her bed and make out, the last couple of times in particular I have put my hands down her pants, (she hinted that she wanted me to do this) but as we make out and I finger her, she puts her hand on my upper leg and sort of reaches for my zipper, at this time I nudge her back on the bed, and just try to pleasure her more to try and avoid her getting in my pants. ( I hate having to do this). I am just really worried because, being 16 (she is to) and my foreskin can't be fully retracted because the part of skin connecting my meatus (I think it's called) to my shaft is a bit short. I'm positive it's not my foreskin being too tight, but definitely that bit of skin, I think it's called a frenulum but not sure if that is correct spelling, but otherwise nicknamed the "banjo string" is too short. This concerns me a lot, that she will go to give me a blowjob or hand job, she sees my penis and gets put off all together, or just puts it back in my pants. What should I do? I have heard that stretching sometimes works, can anyone give me any stretching techniques or methods that I can do. I am really embarrassed about this and prefer not to tell my folks or see a doctor.