Why does my period start and then stop and then start again.

[xoxkxox]

Hi,
I'm 18 and ive had my period for 6 years.i am overweight and i wouldnt say have a healthy lifestyle. My periods were never regular and i always had a heavy bleed and painful cramps. For the last 6 months or so ive had fairly light periods every 6 weeks or so. I find it very hard to keep track of them because 1. it starts and goes on for about 7 days but then about 2/3 weeks later i have a bleed for 2-3 days. I dont know then whether this is the start of a new cycle or if there is something to worry about. as it stands im just ignoring the bleed in the middle and counting my cycle as 38 days. This month my period started on wed evening....very light pinkish bleed...i woke up thurs the same light bleed. thurs afternoon nothing. thurs night nothing. fri morning nothing. friday evening it came baack again but again very light. This morning its heavy enough with black clots. I was at the doctor yesterday because i have an infected sebaceous cyst on my bikini line....i also had cysistis 2 weeks ago which seemed to cure its self when i took cystapurin. Ive had alot of pelvic pain since...mainly on my right side...sometimes its sharp trobbing pain other times its just pressure. The doctor tested my urine and said i have blood and protein in it and i hav a kidney infection. So she gave me augmenton duo antibiotic for the infected cyst and kidney infection. She also took blood to test my hormones and see whats going on with my periods. My main questions here are why does my period stop and then come back then stop again etc and may i have a womans health disorder? My biggest fear is that ill be infertile!
THanks,

[xoxkxox]

oh and by the way im not on any birth control pills and i never have been