People tend to be very all or nothing about veganism or vegetarianism, but in ethical terms, the more meat and dairy we cut out of our lives the better, so that mentality isn't necessarily helpful. Otherwise you might lapse once, think "fuck it" and go around gorging on the flesh of dead animals for the rest of your life because you feel you have failed.....
My best friend is vegan and very occasionally lapses for real cheese pizza. I don't stop thinking of him as a vegan, because that is his intention and what he is, in the main.
It's a bit like lapses in sobriety. If you start to believe that any lapse means you've fucked your sobriety totally, the impulse is to lapse and think, yay, well I've fucked up now anyway, give up, go back to vodka for breakfast, and be briefly happy, then dead.
More helpful to think, even if I have one drink after 12 months sober (or whatever), the second drink remains just as serious a choice as the first, because all that time was NOT wasted....
Does that make sense? I feel very strongly about this. Thinking in absolutely is often harmful to our resolve, counter-intuitively.
So yes, you can have your cheese triangle and still be a vegan, as far as I am concerned, anyway! We all do what we can. Perhaps you body IS telling you something that you need.....