I need help or advice

Since my pprom of my twin boys 01jul2016 I have had to periods. One was 31 day cycle. The second on I'm currently on lasted 43 days. I did test several times for pregnancy but test results were negative. The period I am having today sucks. I should of been close to ovulation on. My old schedule. But now I have a period with lower back pain that makes u feel like u have to poop. Same as the pprom. How long did it take for everyone else to go back to normal on their cycles. I'm used to being 27 days. I want to get pregnant again but don't know how to tract these very different cycles