Well, clearly the foreskin is
supposed to be able to be retracted, so retracting it is not "unnatural".
You can see from comments here both recent and much older, that getting soap under the foreskin is
potentially a major problem, all the more so if you cannot retract your foreskin to wash it out again.
On the other hand, you need to be very careful about the power of
words. "Phimosis" means nothing more than a tight foreskin, it is not a "medical" problem in the vast majority of cases and of course, "balanitis" (or "balano-posthitis") means
inflammation of the glans and/ or inner foreskin which is as often as not simply a manifestation of a form of
dermatitis, not as is so often presumed, an infection.
So the
first thing to be done is to remove any soap by rinsing under the shower, holding the foreskin in a "pout" (as per the picture you will find
on the previous thread) to let the water flush in. This on its own would probably let matters settle, but you might care to try a protective and soothing preparation, my favourite Zinc and Castor Oil cream available from any pharmacy and generally sold as "nappy cream". When you think about it, it makes sense that what you use to protect babies' genitals and such from irritation would be equally appropriate for adults.
Seeing a doctor would likely be considerable overkill for this. As for the stretching, well, just read back through the discussion threads here -
many of them - to understand the
two exercises you need to practice. The first one - stretching the opening - you will actually start by using your finger to introduce a little of the Zinc and Castor Oil cream down the "funnel" demonstrated in that picture and wiping it onto your glans (penis head). While in there, you can check that you can feel all the way around the glans to the back ("corona") except for where the frænulum is on the underneath. Because your frænulum
will be a little short, you need to do the second "exercise" to stretch it as well.
And finally - your girlfriend. I am not sure quite what things you might have practiced already, but I don't see it in terms of "letting her down there". My
strong suggestion would be - immediately - to explain in detail what problem you have had,
show her what is happening at the moment, also your discussion here and what you are doing to sort matters, and once you have the "balanitis" sorted, discuss the aesthetic implications of oral pleasuring at which point you most certainly
should consider - together - how this corresponds to the aesthetics of giving
her oral pleasuring; since whatever there
might be unpleasant about your foreskin, must de facto apply more than double to
her genitals.
As to embarrassment, I put it to you that if you are embarrassed, you do not
have a relationship, and should not be indulging in sexual practices. Think on it!