Hi throwawayaccount
To me, I'm reading it as you felt this to be a truely humiliating, degrading, hurtful experience..........I'm
not saying you have to feel that way, but I am sorry if you do

And the way I see it, is that it says much more about your sister than about you.........I don't know whether she realised the gravity of her actions
or not but she
did "overstep the mark"...........
To me there isn't even an issue here of whether you were/could have been physically stronger than her or not.........that is
not a sign of mascalinity/being a man in my eyes...........as for saying what she wanted you to...........well you wanted it over, right?!! Her behaviour was "
unacceptable" and you wanted it to stop!! You
did see no other way out, so you did/said what you did, that's completely understandable

The vomitting.........well you probably had no end of emotions running through you at the time, right?! Humiliation, degradation, loss of control, helplessness, hopelessnes.........that can be a natural human reaction

And, back to...........this is about her behaviour,
not a reflection on you........so please, please, please try
not to be ashamed!!
And from here.........I don't know if you may want to tell your parents, to tell your parents about any concerns about her behaviour/s, to talk to her about it, to think about how you may be able to set more boundaries for her.......but please try not to be ashamed.
Lastly..........I don't know whether this may be relevant or not..........but if she had an idea of the gravity of her behaviour........or maybe even if she didn't (?)......do you think maybe she has some problems going on for her?? Problems maybe you or your parents could support her a little with??
And obviously I have no idea what they may be,
if she has, but considering her behaviour..........maybe worth a thought??
Last word/s!! No you absolutely
aren't a loser!! And with the issues with depression, I hope you stick around because this is such a supportive community and hoping it/we can help you a little with those
Alison