Hi, PMSing, I get it girl! For years it ruled my life, and in some ways it still does, but I'm starting to out-age it. That's probably not comforting now, but it does ease up with age. Meanwhile, having the self-awareness that you do have about your thoughts and actions is positive and great, so good for you! I completely empathize with feeling irritable, emotional, and saying "mean" things, and like you, being able to label it PMS has also helped me to "order" it within myself. Ya know, knowledge is power and PMS is a very real and daunting thing. Over the years I have tried various herbal remedies for pms and women's hormonal health issues and some have worked great to support me. If you can make it to a health food store like Whole Foods or the equivalent, you'll find a PMS blend of herbs in either capsules, tinctures etc. These can help a lot, but if you also have a mental health issue like me, I'm spectrum bp, herbal remedies have only gone so far; it's my meds that have made the real difference. I'm definitely a proponent of holistic healthcare in conjunction with traditional western methods of treatment and medication. Maybe check this out. Also, Acupuncture and Chinese herbs are super effective if you can afford it.
It sounds to me that you may be putting too much on your plate right now too; maybe just focus on school in the fall and getting settled for that, which is huge enough. If a job is necessary then focus on that and let the volunteering go for now. I know for me that overloading just adds emotional pressure and sets off my irritability and stuff. You are super bright and you want to do a lot and you will, but balancing yourself emotionally i feel is the foundation for all you want to accomplish. Can you pull back a little bit? You said it's overwhelming, which is enough to make anyone unhappy. While you're looking for a therapist, maybe a group therapy would be beneficial. Also, when you start school in the fall, look into their psych services. They may have peer therapy groups as well private therapy. Most colleges and universities do. One last thought, writing has always been therapeutic for me; I keep a journal and write poems and such, and it doesn't matter if they're good or not. Look in your community for creative writing workshops targeting emotional healing, or just keep a diary and postings here