Thanks Kitty and English. Just googled my question and found this well of information www.amandabears.com/faq.html#.Uv8kTH8aySM
This bit is v interesting and answers the question I think, basically pms caused by progesterone rise, which will always occur after ov regardless if fertilised egg or not, so PMS can come as usual (hope);
Q. What is progesterone and what role does it play?
A. Progesterone is a natural hormone in our bodies that we produce after we ovulate. Once the follicle releases the egg, the Corpus Luteum produces progesterone. Progesterone is important because it prepares the uterus for pregnancy, and sustains a pregnancy. Progesterone is the reason behind your typical pms symptoms. There are reasons why you feel progesterone symptoms more than others each cycle. This is because each cycle, each luteal phase (time after ovulation) your Corpus Luteum will produce a different amount of hormone each time. For an instance, let's take cycle 4-
On cycle 4, Lucy had her progesterone level tested (known as a P4 level) at 7 days passed when she think she ovulated. Her level is tested through blood test, which ended up being 17.6mL. Lucy is feeling her typical progesterone symptoms this cycle.
However on Cycle 5, Lucy has her progesterone levels tested again. This cycle during the luteal phase her level is at 22.9mL. This cycle she is feeling stronger progesterone symptoms than last. Her breasts hurt a lot more, she has gas/bloating, she is more tired, and her appetite has increased.
Does this mean Lucy is pregnant, no, this just means her Corpus Luteum is producing a different amount of hormone from the last cycles. Once her embryo implants however, her progesterone may go up and elevate, as well as her estrogen and of course HCG.