Well, I've always been irregular, like u, i would skip weeks, months and my pms has always been all over the place. Since I was getting pms, but not bleeding, after 6 months, i thought maybe i had a tumor blocking the way. So I went to the dr and they did all kinds of tests of me, I dont remember them all, but a pap, tested my blood, tested my thyroid. Nothing was wrong. So they put me on some pills (i dont remember what they were) and i was to take them for a time frame, like 2 weeks i think and they said on day 15 i would start. So as time comes closerr, i feel pms-y and day 15 comes and NOTHING! So I go back, by this time its about 8 months without a period. So, they put me on pure Estrogen pills for 40 days straight! I kid you not, this was about the worse time in my life. I was crying everyday, screaming, irritable, and very suicidal. I had the appetite of a pregnant woman and put on 10 lbs in a month and I normally dont gain weight easy. (Once I was driving on the freeway and the radio in my car went out, I started crying soooo hard I couldnt even drive. I had to pull over and i was crying like mad forever. I had to drive back home and cancel whatever it was I was going to, I dont remember) Stuff like that happened like everyday.
Anyways I did start in 40 days. They put me on the pill and my periods became regular and my pms went away, and my complexion has never been so beautiful. but after about 3 months, I couldnt take it...the depresssion was just as bad and I was gaining more weight. My sis said to try another pill with less estrogen, but for fear of harming myself, I said, forget it, I'll take the pms and the irregular periods.
It's been like 2-3 yrs since i went off the pill and my periods have been almost always regular, i'm amazed! I still get pms, but i think as i get older (i'm 29) its getting somewhat better, but some months are cool, some months, i cant even bear it.
So, the pill is great for regulating periods, most my friends are on it just for that reason. But its not for everyone; i'm prone to depression and i dont care if they have lower dose super pills (my sis encourages me to get on them), but she doesnt experience the depression I do and doesnt understand. But I know me and its not worth my life.
Hope I answered your question somewhere in there

. In fact, I JUST started while writing this, right on time too.
BTW, I know one more thing that makes u get your period. If u want to know, let me know, its kind of gross, but it works (its nothing bad), but it has to do with pheromones. Are you still awake?.. sorry this is soooo long. Take care!