Caffeine definitely is not the cause of my BPD symptoms, but a shroom trip with just 1 gram helped me realize that I do have a caffeine addiction which negatively impacts my life. I think I have been denying it, saying to my self that - it's just caffeine, it's not like I do drugs. Shrooms helped me accept that brain biochemistry doesn't care about the legal status of caffeine. I had to accept that even though being completely legal and sold everywhere, I do get mood crashes from caffeine as I would from cocaine (which I tried about 12 years ago). I can have a few cups of tea in a day, but I do like to drink several in a row, I also like coffee and yerba mate. I have been observing my symptoms for a while and I do notice that I get dysphoric later on in the day if I have coffee or yerba mate in the morning, especially on an empty stomach. I also get more paranoid about being alone, not having any friends (even though I do have several good friends), etc. I knew this for a while, just shrooms helped me accept that I really should do something about the caffeine addiction as it really negatively impacts my mood and sense of self.   
I don't think I need to completely give up tea, but I did have to quit coffee and yerba mate, which actually did help me to have a more even mood throughout the day. I also have been taking CBD oil that I made at home, I think that also helps with anxiety and mood swings. I will still have a few cups of black tea, which I love, but I need to limit myself at only three-four cups of tea per day, not very strong.