My advice for what it's worth is have lots of 'patience', if she wants or needs to be alone, don't be insulted, it's not personal against you, it's just that sometimes the pain is really intense, even with pain killers and it's exhausting having to do anything, plus the pain killers too can make you really lethargic and dopey. Rest and sleep at weird hours of the day as well as night, are needed. So if she's not up to socialising, or events that you have booked or bought tickets for, please don't push her in to doing something that she really isn't up to coping with. If she can manage to go out, I'm sure she will. Otherwise watch a movie curled up on the sofa or in bed is going to score high marks. Distractions that don't use up energy and effort are always good.
As jayden said, preparing meals or getting a takeaway and doing washing up for her on bad days will certainly endear you to her. Just standing up in the kitchen to do basics can be incredibly painful when in the full throws of a painful endo episode.
but don't over do it (household chores wise) and make her feel even more guilty that she can't manage to do things for herself at that time. Unless you do particular chores the rest of the time too it looks too obvious if the only time you do these things is when she is not well and that adds to the guilt she will feel for being not up to it anyway.
A gentle tummy massage of the lower tummy can be a wonderfully soothing experience, if she has cramping pain,
e.g. place WARM hand across the space between one hip bone and the other,
with the side of your hand lined up with the jutting out hip bones, so your hand covers the ovaries and womb area.
Just gentle rocking a hand over that bit of the tummy back and forth or side to side rocking
or round like press down fingers, then side of hand, then wrist, other side of hand in a circle motion a few times then reverse the direction of motion).so long as you are absolutely not looking to take it further if you know what I mean.
A vigorous massage of the tummy is actually going to injure and cause more endo problems and prolong the bleeding and probably encourage more adhesions to grow, so don't bother getting all technical with a Thai or Turkish Massage or anything fancy you might read about in books or online. Just very slow deliberate movements pressing down in to the lower tummy will help keep the muscles from cramping too much.
Can be done directly on the skin or over clothes.
Cuddles and Hugs are also usually welcome, so long as that is as far it goes when she's in lots of discomfort, be content that you're helping her a lot, just by being there and a cuddle without expectations of anything more is 10/10 in the being supportive stakes.
Or a foot massage or shoulder or back massage to distract from pain elsewhere can be a good idea too. Or if she has shoulder length or longer hair, something as simple as brushing her hair or running your fingers through her hair like you are combing it by hand, can act as a pain distraction.
Othertimes the pain is very tender and sore and massaging it is not going to be the best idea.
Hot aromatherapy baths can be great for relaxing, but if she's having a heavy bleed that might be the last thing she wants.
Communication is essential. If you're not sure what she wants or doesn't, then ask but don't demand answers.
If she feels the need to nap or sleep, have some consideration, keep the tv noise down, don't start hoovering the house or having rowdy friends over.
Do NOT keep asking how she is feeling - she will feel like crap, she knows it, you know it, and yet she'll probably still say she's okay. It's what all women do instinctively.
So if you are texting her or calling her, the 'How are you?' questions should be kept to an absolute minimum. Best avoided if possible, or put some imagination and humour in to it. e.g."Scale of 1 to 10, what's today's score?"
When i'm going through a bad spell, to be honest i don't want to do much if anything. I just need time and space, pain relief and sleep to get through it till it's over enough that I can get back to 'normal' activities. I don't need other people fussing over me all the time, that uses up my precious energy resources, I don't need a guilt trip or snide jokes if i'm late or forgotten to do something, I just need understanding. If the shopping hasn't been done, or the laundry hasn't been ironed so what ! it will get done eventually.
If I say I'm not up to going out then just leave me be. No big deal, I don't stop others going out and enjoying themselves, and for me, I'd rather they were out of the way to be honest, and leave me in peace and quiet most of the time.
Some ladies might prefer to keep their chaps at home, and some chaps might prefer to stay at home.
I'm sure your girlfriend probably has a routine she is used to, for times when it's bad, it's just one of those things that we have to get through and get used to. It's hard on both partners in their own way.
You sound like a very caring chap, and she's lucky to have someone willing to be so supportive from the start. I wish you both all the best.