Advice please

Hi everyone this is my first post asking for advice and help. I'm am also very shy and nervous about this so please keep the negativity to a minimum.

Here goes.....

My husband and I have been ttc for a year and a half now, but the last few months my periods have been way out of whack with no real reason. Tests come up negitive and now my husband has just not been interested in sex at all and doesnt even want to try anymore. he went finish inside me and he doesnt even care about finishing me off anymore. the questions are pretty obvious but, I'm I doing something wrong to cause him to change this drastically. He was the one who wanted a second child but now he has changed. I don't know what to do. please help.