Why do i get like this?and snap and say hurtful things to my lovely boyfriend?

there r 2 sides of me : confident, assertive funny and considerate. But( every week it seems) i let small things get to me, frustrate me, to the point of crying wherever it may be. and days when it is fine. as for my kind levelheaded boyfriend, i can snap at him tho he wouldn't deserve him, and it works in a crescendo in my head where i can't relax.a few times a month, i get very sad thoughts in my head like how it'd be so simple if i didn't exist anymore...
i have had these since i was a teen, i am 27 now. and seemed to have noticed it more now that i have a serious boyfriend, someone to hurt. before i'd just be harsh on myself, which i still do.
i want to know where i could get a mental health screen test or similar diagnosis to see if i can prevent that, i don't want to end up like Betty Blue....

my sex drive goes up and down, and of course i have never been able to come( except with myself, all the time). my mind cannot relax enough...

I thought I would post a message, not because I do the same, but because I am on the receiving end of something identical. It is often very hard for me to deal with, but I can appreciate that it is just as hard for her too. I deal with it some days better than others. But something that will always remain true, she is the most amazing and exciting person I have ever met, and she will always mean to the world to me. I just wish that she would open up to me a bit more, so that I can maybe help, so my advice is to perhaps just chat to your boyfriend a bit more. He must care for you a great deal if he is able to see through your 'moments'. I'm sure there are many forms of help available out there, as suggested by other people here, it certainly sounds like it is worth a try.
Don't lose sight of the fact that your boyfriend loves you!

I dont really know the answer but i will be watching your question for answers. I do the same thing to those close to me. Even my best friends. They have stuck by me however, and are use to it, and know I will apologize in a few hours after i have calmed down. She calls it my 'cycle'. I can understand how unpredictable it is and you can't control that you are doing it and really wish you don't but it just comes out. I can say some really hurtful things when i get like this and i honestly dont mean a single one of them. . . i'm glad im not alone.

I am the exact way. I think, for me, it is a combination of horomones and serotonin levels. Birth control pills are good at controlling horomone related mood swings and SSRI drugs such as Prozac, Zoloft, etc. work well on the serotonin.

When it comes to your boyfriend, you need to let him know you can't control your outbursts. You need to talk to him about this whenever you are levelheaded, and apologize to him often. This is my experience, and somehow my boyfriend loves me in spite of my unpredictable temperment.

You should seek counseling. If you have one, ask your clergy to recommend someone or ask your doctor. Or check with a good hospital who can recommend who to see.The right help and proper medication could turn your life around. Good luck and God bless.

diagnosis: *****

It sounds a lot like borderline personality disorder. Kudos to you for recognizing your situation. I think a mixture of medication & cognitive behavioral therapy would be a good way to go for you. Keep in mind....., there is relief for what you suffer from. It might not be total relief, but there's relief.