I think youre unnecessarily getting a pasting.
Surely it's no surprise? Any time a man posts here, women flood to be patronising and always do their best to make the man feel he is wrong, somehow, even when there's no problem on his part.
It wouldn't be MN without the double standards. As I often say, it's not surprising, but it sure is a horrible aspect of this site and one that needs to be called out more often.
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OP, I assume she was upset by her friend but it must have been a build up of all her feelings towards her and it just came to a head last night for her. I can completely understand you not wanting to leave her whilst she was upset, it almost presents itself as a situation where if you had left she would have said you don't care and left her for your friends when she was upset.
Let her sort her friendships out, just offer to listen when she wants to vent. Unless she specifically asks for advice, don't give it, let her figure her friendships out and what she wants for herself.
As for the blood thing, you are not unreasonable for this, no one should be pressured to have sex if they feel uncomfortable with something.
In regards to her overall mood, the medication will have a specific impact on her but it's not an excuse for poor behaviour towards you. Therefore you will need to establish where you draw a line. Consistently just being off towards you and taking anger out on you is wrong and there's no need for you to be her punching bag. Had you been a woman mentioning a sulky or moody boyfriend, you would have been inundated with messages saying it's not worth it and LTB.
Discuss what is concerning you and ask her if she feels her medication is what she feels is causing her mood to be down recently, if she feels it is, perhaps she should go speak to her GP and see what else is available. Whilst that is all being addressed, I do suggest you wear a condom despite what you prefer, it's just the sensible option.
I'm not sure how long you've been together, but if she is usually a happy person, and there has not been issues, she might evidently be going through a difficult time and quite possibly cannot even explain what's wrong as she herself is confused. Just be a bit patient and let her know you are there for her and she does not need to talk but just find comfort in knowing she has someone who does value her.
We all have times in our lives where we get down and it can be a couple of things and it could simply be something that does not have a solution but just something that needs to pass.
This just requires some patience from your side for the time-being, hopefully things get better soon.