I dont know what to do, i feel almost hopeless

I've always been a happy person, when I was little I would go through bouts of loneliness or fear of one thing or another, but they never lasted long, I've always tried to be positive and I love my life, I've never wanted to change it. About two months ago I hit PMS for the first time at 15 a week or two before my 16th birthday it wasn't bad, I thought it was passing because it only lasted for a day, but it happened exactly a week before my period. The next month the exact same thing happened, a week before my period I got bad mood swings and felt depressed, especially about my relationship that I love and have never had doubt's about before, now what was so different was that that month the feeling of being depressed about something followed me through the whole month, even though it wasn't as strong, and now, a month later I have gotten what seems to be bad PMS depression and mood swings TWO weeks before my period, and I can't help feeling like I'm going completely down hill. I don't know what to do, and I'm dreading ruining my relationship with the guy I love and never being able to fix it. This feeling even makes me doubt if he is the right person for me, even though before it started I never had a doubt, I feel trapped and I fear I'll never get out of it. On the month where it first started getting bad, I started taking this herbal mix of stuff that someone recommended me, but could it make it worse? I was wondering because my PMS symptoms didn't stop throughout the month.

I'm not really sure what I'm looking for, comfort, reassurance that someone else has felt like this, I don't really know, but here it is.

P.S. please don't just say I need to go see a doctor, I've heard a lot of stories about how that just doesn't work