Pregnancy and periods. Plz guide.

Want to get pregnant but not able to, everymonth we think I am pregnant as the period gets delayed by 10 days and I have 40 days cycle now before it was always 30 days cycle. Since I have married, the cycle has got disturbed when we thought of starting pregnancy, the first it so happened that I didn't get my periods in the month of June then it started with spotting after 12days of the actual date of periods and then it came full fledgedly after 10days  of spotting and we thought ok now next month we didn't try as we were no together and then we tried in September that time also I got delayed periods of 12days that time again in oct the same thing happened and everytime we think I m pregnant it comes, everymonth we have the same story and we have got tired of it. I am just 29 and not able to get pregnant got the ultrasound report also, it was ok nothing weird was found, husband has all the things right he got tested then what else do we need to do. I just don't  understand. Plz guide.