What Causes Irregular Periods?

I haven't seen my period for about 8 months now, and to top it off, I think I have a vaginal infection or STD. I'm seeing three different color of vaginal discharge in my underwear: white, yellow, and brown. But most recently jus yellow and the brien and the scent is getting worse. U also have series of belly cramps. I really scared because I have had yeast infections but not this bad and I'm worried that I nay be getting worse. Oh, I have irregular period but I'm wondering if it's the vaginal infection or STD that makes me not see my menstrual for so long. I'm 21 years old going on 22 in April. One more thing does this means I'm not going to have a child