Best Advice of all was to enjoy yourself first,
better than that you should be really mad at her for her lack of understanding.
Really show her and tell her that it is definetly not ok for her to be mad at your
for not gettin it up when you was stressed, cos of being tired and late AND eating her out.
God damn , you was giving her oral pleasure so what the fuck she is complainin about. Make that clear that u will not accept such lack of empathy bull shit behaviour from her or anyone anytime ever at all. Just be dead serious about it, say it affected you on a much deeper than sex, "human" level and geniuinly hurt your feelings.
If you don't do this, she will continue to have the sexual power in your relationship and you will continue to have the totally unnessasary urge to please her first despite of your own needs and your own sexuality.
I mean: YOU ARE THE MAN DON'T BEHAVE LIKE A WUSSY. You already ate her out ( wich she should be more than grateful for and not complaining and acting pissed of) , so what if you as a man who is feeling tired decides to call it quits , turn around and sleep.
The sooner your realize how and why woman even at young age manipulate the living fuck out of any man and how to counteract those manipulations - the sonner you will become agrown up self-confident self-secure-in-any-situation- kind of man.
Its not that women are evil in general or your girlfriend is especially mean or bad. Its SIMPLY completely natural for them a unconciuos biological drive for the female to test and test , and retest (in neverending loops) if her partner is the best MALE for her (as in best father for her children).
The manifestation of this in your/the real world is/was her lack of understanding stupid bitchy behaviour. Deal with it in a manly way. Be a man about it - its extremly important for your future relationship.
If you can handle any situation (even a scenario like this) being cool about it and secure and NOT shit your pants and do anything possible to again please her and teach her the wrong lesson as in : YOU HAVE ALL THE POWER OVER ME.
Don't give away your power , my friend - Only you can know what is best for you , no one else will.
Ok 2nd solution (If you are to young to understand why what I said above make a lot of sense) :
By that viagra throw in 50 mg 1hour before sex and fuck the crap outta her...
don't worry about people here sayin: do you want to become dependent on it.
You probably will become dependant on it - but hey you depend on so so sos so many things like the right food , water , sport, healthy environment , parents , friends (YOUR GIRLFRIEND
^^ ) so who cares about one more or less dependency...if it gets the job done for you...eh ?? Besides if viagra is well tolerated and you can deal with the sideeffects its pretty good for your health..training your heart and cleaning your arteries..improoving circulation everywhere...
But its up to you to decide - the better solution is definetly to reeducate your girlfriend so that HER and YOUR life will improove through better communication and understanding for each other than JUST YOU throwing in pills in order to pretending to be good enough for her - where is your self respect ??? Probably 7 Billions People on this planet half of dem female -
who told you, what make you think , this girl is THE ONE AND ONLY , thats bullshit, there are thousands alike , worse and mcuh much much better...
Peace
Tbirdy