Hi op, we sound very similar and I wanted to say firstly that based on my experience I would avoid the pill. I tried it (not actually because of my moods, but because of period pains/heavy & irregular bleeding), and though it was fine for the first month or two, it became horrendous. Think of the very worst, lowest, angriest, most paranoid etc version of yourself that you feel before your period starts - and I was like that every single day. I knew something was wrong with me but it took me a long time to recognise that it was the contraceptive pill that was the problem. I nearly lost my job at the time and did lose a boyfriend because of my behaviour/mood swings. Once I finally realised the pill was the issue, I tried a few different types of pill, and it all ended the same way. I googled it at the time and read story after story of others who reacted the same way to it and I personally would never touch hormonal contraceptive again. I know you could be fine with it, just something to consider. Oh and I had a similar experience (though not as extreme) with evening primrose oil, but some women swear by it.
Now not on the pill, I've worked really hard to recognise in myself when it is my period altering my mood and though I can't entirely control it, I am a lot better in how I relate to my partner especially.
I will try to explain what I do and I'm sorry in advance because this is going to sound absolutely mental.
So the starting point was recognising that my mood was changing every month before my period, and sort of acknowledging to myself that something was going wrong there. it's progressed to now where at that time of the month it's as though I have two voices in my head, the crazy PMS woman and my more normal rational self. And I try to be open with my partner about what's going on.
For example, say my crazy brain is telling me he doesn't love me because he did something outrageous like said goodnight (genuine example of something I've freaked out about and I'm not proud). So I now have the two voices in my head - crazy, (he doesn't love me, he said goodnight in a cold way, if he loved me he'd make sure I was ok before saying goodnight etc )- and rational, (it's 11pm, he's tired and needs to sleep, he said goodnight normally, this isn't you (me), this is your hormones talking). I'm trying to figure out which of these two voices is the true voice, which is correct, and so on... And I've started to tell my partner all of this. I say to him, "my brains telling me you don't love me because of X, but my other brain is telling me this is my period and I don't know what's true. And we have a big long conversation about it, and God I know this sounds absolutely mental but it really has helped/is helping me. My partner is so understanding about all of it, my moods, the general insanity of it all, and I am really lucky in that respect. It is still a work in progress but it's really helped and I've got better at slowing down before I react to things too because of thinking
Something that I haven't been able to fix as of yet is that I will have at least 1-2 nights where I can't stop worrying. I lie in bed not being able to sleep with worry after worry running through my mind. Worried about the future, worries about things that happened in the past and so on. It's awful and I feel like I'm torturing myself, but I'm glad I'm mentally beating myself up rather than my loved ones. And also, less bad then the moods but an annoying physical symptom is that I vomit the night before my period starts. I'm not really sure why this is, it's not from pain, I assume it's hormone related though.
Outside of this time, I'm actually a pretty easy going and happy person. It's pretty shit having to go through this each month but I am hoping to keep on working at it.
Anyway this is far longer than I intended and I have made myself sound absolutely insane, but I hope it helps in some way.