Do Diet And Exercising Cause Missed Periods With Prolonged Spotting?

I am 30 years old and my cycle has always been semi abnormal. I have skipped occasional periods before. I should have started my period around the end of May or early June but it didn t come and then on June 18 I started spotting. There was a lite flow for a while but it didn t really even require use of tampon or panty liner. The color was either red or dark pink. Now 16 days later I am still spotting. It has slowed down almost stopped but still having pink spotting and occasionally red. I am overweight and started diet and light exercise this month so I have lost about 10 pounds in 4 weeks. Can my change in diet cause this problem. Last year I had 2 cycles where I had lite spotting for a day or two between cycles but not like this.