I'm a bit confused!! I'm 20 and I have a 3 and a half yeah old daughter. I've always had a reggular 28 day cycle. Well this was up until 7 months ago, now my cycle can be anything for 30 to 40 days, me and my partner have been trying for another baby for the past 6 months. My doctor wants me to go for blood test what are the blood tests for? And what could be the reasons my periods have gone so irregular?

There are many reasons your period may have become irregular, stress, diet etc. Most likely it's a disturbance in your hormone regulation, your doc is right in taking blood test where they will measure the levels of lh, fsh, which are basically the hormones that allow you to produce an egg and to ovulate and get pregnant if the egg is fertilized by the sperm.

Another common disease that causes irregular periods is PCOS, but I am not a doctor and cannot diagnose you so its best to just do the blood test.

Polycystic ovary syndrome - Wikipedia, the free encyclopedia