I'm almost 39weeks pregnant and i recently noticed a tender knot/lump in the skin at the bottom of my belly?

Hi, I have exactly the same thing! A little below my belly on and its a lump...I think its very common and from where the skin stretches...a little like scar tissue. I have stretch marks all across my lower belly like you and think its just the trauma of having so much stretching in such a short space of time. If you are concerned about it then I would definitely tell your midwife or doctor and put your mind at rest but I'm pretty sure its fine and another one of those lovely things from pregnancy :P Good Luck and hope all goes well :)