Hi

"I have heard of implantation spotting but I'm confused as to what exactly it is and when/how it happens. Any further thoughts would really help! That is my biggest fear at the moment."
Satine-I am no expert, but I believe implantation spotting is the temporary, light bleeding that occurs when the fertizlied egg(pregnancy)is trying to attach itself to the uterus.
I would take an HPT to make sure you are not pregnant. If you're not pregnant, then I would not worry too much about it. Our periods are very volatile and can change on you at the drop of a dime. Or you can always call your doctor and have him/her check it out.
Let us know!